NTFS is supported in other desktop and server operating systems as well. Linux and BSD have a free and open-source NTFS driver, called NTFS-3G, with both read and write functionality. macOS comes with read-only support for NTFS; its disabled-by-default write support for NTFS is unstable.

In the mid-1980s, Microsoft and IBM formed a joint project to create the next generation of graphical operating system; the result was OS/2 and HPFS. Because Microsoft disagreed with IBM on many important issues they eventually separated: OS/2 remained an IBM project and Microsoft worked to develop Windows NT and NTFS.

The HPFS file system for OS/2 contained several important new features. When Microsoft created their new operating system, they borrowed many of these concepts for NTFS.[8] NTFS developers include: Tom Miller, Gary Kimura, Brian Andrew and David Goebel.[9]

Probably as a result of this common ancestry, HPFS and NTFS use the same disk partition identification type code (07). Using the same Partition ID Record Number is highly unusual, since there were dozens of unused code numbers available, and other major file systems have their own codes. For example, FAT has more than nine (one each for FAT12, FAT16, FAT32, etc.). Algorithms identifying the file system in a partition type 07 must perform additional checks to distinguish between HPFS and NTFS.

v1.0: Released with Windows NT 3.1 in 1993.[7] v1.0 is incompatible with v1.1 and newer: Volumes written by Windows NT 3.5x cannot be read by Windows NT 3.1 until an update (available on the NT 3.5x installation media) is installed.[10]

v3.1: Released with Windows XP in October 2001 (and subsequently used also for Windows Vista and Windows 7). Expanded the Master File Table (MFT) entries with redundant MFT record number (useful for recovering damaged MFT files). Commonly called NTFS 5.1 after the OS release

The NTFS.sys version number (e.g. v5.0 in Windows 2000) is based on the operating system version; it should not be confused with the NTFS version number (v3.1 since Windows XP).[13]

Although subsequent versions of Windows added new file system-related features, they did not change NTFS itself. For example, Windows Vista implemented NTFS symbolic links, Transactional NTFS, partition shrinking, and self-healing.[14] NTFS symbolic links are a new feature in the file system; all the others are new operating system features that make use of NTFS features already in place.

NTFS v3.0 includes several new features over its predecessors: sparse file support, disk use quotas, reparse points, distributed link tracking, and file-level encryption called the Encrypting File System (EFS).

NTFS is optimized for 4 KBclusters, but supports a maximum cluster size of 64 KB.[15] The maximum NTFS volume size that the specification can support is 264 − 1 clusters, but not all implementations achieve this theoretical maximum, as discussed below.

The maximum NTFS volume size implemented in Windows XP Professional is 232 − 1 clusters, partly due to partition table limitations. For example, using 64 KB clusters, the maximum size Windows XP NTFS volume is 256 TB minus 64 KB. Using the default cluster size of 4 KB, the maximum NTFS volume size is 16 TB minus 4 KB. Both of these are vastly higher than the 128 GB limit in Windows XP SP1. Because partition tables on master boot record (MBR) disks support only partition sizes up to 2 TB, multiple GUID Partition Table (GPT or "dynamic") volumes must be combined to create a single NTFS volume larger than 2 TB. Booting from a GPT volume to a Windows environment in a Microsoft supported way requires a system with Unified Extensible Firmware Interface (UEFI) and 64-bit support.[16]

NTFS is a journaling file system and uses the NTFS Log ($LogFile) to record metadata changes to the volume. It is a feature that FAT does not provide and critical for NTFS to ensure that its complex internal data structures will remain consistent in case of system crashes or data moves performed by the defragmentation API, and allow easy rollback of uncommitted changes to these critical data structures when the volume is remounted. Notably affected structures are the volume allocation bitmap, modifications to MFT records such as moves of some variable-length attributes stored in MFT records and attribute lists, and indices for directories and security descriptors.

The USN Journal (Update Sequence Number Journal) is a system management feature that records (in $Extend\$UsnJrnl) changes to files, streams and directories on the volume, as well as their various attributes and security settings. The journal is made available for applications to track changes to the volume.[17] This journal can be enabled or disabled on non-system volumes.[18]

The hard link feature allows different file names to directly refer to the same file contents. Hard links are similar to directory junctions, but refer to files instead. Hard links may link only to files in the same volume, because each volume has its own MFT. Hard links have their own file metadata, so a change in file size or attributes under one hard link may not update the others until they are opened.[19] Hard links were originally included to support the POSIX subsystem in Windows NT.[20]

Windows uses hard links to support short (8.3) filenames in NTFS. Operating system support is needed because there are legacy applications that can work only with 8.3 filenames. In this case, an additional filename record and directory entry is added, but both 8.3 and long file name are linked and updated together, unlike a regular hard link.

Alternate data streams allow more than one data stream to be associated with a filename (a fork), using the format "filename:streamname" (e.g., "text.txt:extrastream").

NTFS Streams were introduced in Windows NT 3.1, to enable Services for Macintosh (SFM) to store resource forks. Although current versions of Windows Server no longer include SFM, third-party Apple Filing Protocol (AFP) products (such as GroupLogic's ExtremeZ-IP) still use this feature of the file system. Very small ADS (named "Zone.Identifier") are added by Internet Explorer and recently by other browsers to mark files downloaded from external sites as possibly unsafe to run; the local shell would then require user confirmation before opening them.[22] When the user indicates that they no longer want this confirmation dialog, this ADS is deleted.

Alternate streams are not listed in Windows Explorer, and their size is not included in the file's size. When the file is copied or moved to another file system without ADS support the user is warned that alternate data streams cannot be preserved. No such warning is typically provided if the file is attached to an e-mail, or uploaded to a website. Thus, using alternate streams for critical data may cause problems. Microsoft provides a tool called Streams[23] to view streams on a selected volume. Starting with Windows PowerShell 3.0, it is possible to manage ADS natively with six cmdlets: Add-Content, Clear-Content, Get-Content, Get-Item, Remove-Item, Set-Content.[24]

Malware has used alternate data streams to hide code.[25] As a result, malware scanners and other special tools now check for alternate data streams.

NTFS can compress files using LZNT1 algorithm (a variant of LZ77)[26] Files are compressed in 16 cluster chunks. With 4 KB clusters, files are compressed in 64 KB chunks. The compression algorithms in NTFS are designed to support cluster sizes of up to 4 KB. When the cluster size is greater than 4 KB on an NTFS volume, NTFS compression is not available.[27] If the compression reduces 64 KB of data to 60 KB or less, NTFS treats the unneeded 4 KB pages like empty sparse file clusters—they are not written. This allows for reasonable random-access times as the OS just has to follow the chain of fragments. However, large compressible files become highly fragmented since every chunk smaller than 64 KB becomes a fragment.[28][29] According to research by Microsoft's NTFS Development team, 50–60 GB is a reasonable maximum size for a compressed file on an NTFS volume with a 4 KB (default) cluster (block) size. This reasonable maximum size decreases sharply for volumes with smaller cluster sizes.[30] Single-user systems with limited hard disk space can benefit from NTFS compression for small files, from 4 KB to 64 KB or more, depending on compressibility. Files smaller than approximately 900 bytes are stored within the directory entry of the MFT.[31]

Flash memory, such as SSD drives do not have the head movement delays of hard disk drives, so fragmentation has only a smaller penalty. Users of fast multi-core processors will find improvements in application speed by compressing their applications and data as well as a reduction in space used.[32] Note that SSDs with Sandforce controllers already compress data. However, since less data is transferred, there is a reduction in I/Os.

Compression works best with files that have repetitive content, are seldom written, are usually accessed sequentially, and are not themselves compressed. Log files are an ideal example.

If system files that are needed at boot time (such as drivers, NTLDR, winload.exe, or BOOTMGR) are compressed, the system may fail to boot correctly, because decompression filters are not yet loaded.[33] Later editions of Windows[which?] do not allow important system files to be compressed.

Files may be compressed or decompressed individually (via changing the advanced attributes) for a drive, directory, or directory tree, becoming a default for the files inside.

Although read–write access to compressed files is mostly[34]transparent, Microsoft recommends avoiding compression on server systems and/or network shares holding roaming profiles, because it puts a considerable load on the processor.[35]

A sparse file: Empty bytes don't need to be saved, thus they can be represented by metadata.

Sparse files are files interspersed with empty segments for which no actual storage space is used. To the applications, the file looks like an ordinary file with empty regions seen as regions filled with zeros.[36]

Database applications, for instance, may use sparse files.[37] As with compressed files, the actual sizes of sparse files are not taken into account when determining quota limits.[38]

The Volume Shadow Copy Service (VSS) keeps historical versions of files and folders on NTFS volumes by copying old, newly overwritten data to shadow copy via copy-on-write technique. The user may later request an earlier version to be recovered. This also allows data backup programs to archive files currently in use by the file system. On heavily loaded systems, Microsoft recommends setting up a shadow copy volume on a separate disk.[39]

Windows Vista also introduced persistent shadow copies for use with System Restore and Previous Versions features. Persistent shadow copies, however, are deleted when an older operating system mounts that NTFS volume. This happens because the older operating system does not understand the newer format of persistent shadow copies.[40]

As of Windows Vista, applications can use Transactional NTFS (TxF) to group multiple changes to files together into a single transaction. The transaction will guarantee that either all of the changes happen, or none of them do, and that no application outside the transaction will see the changes until they are committed.[41]

It uses similar techniques as those used for Volume Shadow Copies (i.e. copy-on-write) to ensure that overwritten data can be safely rolled back, and a CLFS log to mark the transactions that have still not been committed, or those that have been committed but still not fully applied (in case of system crash during a commit by one of the participants).

Transactional NTFS does not restrict transactions to just the local NTFS volume, but also includes other transactional data or operations in other locations such as data stored in separate volumes, the local registry, or SQL databases, or the current states of system services or remote services. These transactions are coordinated network-wide with all participants using a specific service, the DTC, to ensure that all participants will receive same commit state, and to transport the changes that have been validated by any participant (so that the others can invalidate their local caches for old data or rollback their ongoing uncommitted changes). Transactional NTFS allows, for example, the creation of network-wide consistent distributed file systems, including with their local live or offline caches.

Microsoft now advises against using TxF: "Microsoft strongly recommends developers utilize alternative means..." since "TxF may not be available in future versions of Microsoft Windows".[42]

In NTFS, each file or folder is assigned a security descriptor that defines its owner and contains two access control lists (ACLs). The first ACL, called discretionary access control list (DACL), defines exactly what type of interactions (e.g. reading, writing, executing or deleting) are allowed or forbidden by which user or groups of users. For example, files in the C:\Program Files folder may be read and executed by all users but modified only by a user holding administrative privileges.[43] Windows Vista adds mandatory access control info to DACLs. DACLs are the primary focus of User Account Control in Windows Vista and later.

The second ACL, called system access control list (SACL), defines which interactions with the file or folder are to be audited and whether they should be logged when the activity is successful, failed or both. For example, auditing can be enabled on sensitive files of a company, so that its managers get to know when someone tries to delete them or make a copy of them, and whether he or she succeeds.[43]

Encrypting File System (EFS) provides strong[44] and user-transparent encryption of any file or folder on an NTFS volume. EFS works in conjunction with the EFS service, Microsoft's CryptoAPI and the EFS File System Run-Time Library (FSRTL). EFS works by encrypting a file with a bulk symmetric key (also known as the File Encryption Key, or FEK), which is used because it takes a relatively small amount of time to encrypt and decrypt large amounts of data than if an asymmetric key cipher is used. The symmetric key that is used to encrypt the file is then encrypted with a public key that is associated with the user who encrypted the file, and this encrypted data is stored in an alternate data stream of the encrypted file. To decrypt the file, the file system uses the private key of the user to decrypt the symmetric key that is stored in the file header. It then uses the symmetric key to decrypt the file. Because this is done at the file system level, it is transparent to the user.[45] Also, in case of a user losing access to their key, support for additional decryption keys has been built into the EFS system, so that a recovery agent can still access the files if needed. NTFS-provided encryption and NTFS-provided compression are mutually exclusive; however, NTFS can be used for one and a third-party tool for the other.

The support of EFS is not available in Basic, Home, and MediaCenter versions of Windows, and must be activated after installation of Professional, Ultimate, and Server versions of Windows or by using enterprise deployment tools within Windows domains.

Disk quotas were introduced in NTFS v3. They allow the administrator of a computer that runs a version of Windows that supports NTFS to set a threshold of disk space that users may use. It also allows administrators to keep track of how much disk space each user is using. An administrator may specify a certain level of disk space that a user may use before they receive a warning, and then deny access to the user once they hit their upper limit of space. Disk quotas do not take into account NTFS's transparent file-compression, should this be enabled. Applications that query the amount of free space will also see the amount of free space left to the user who has a quota applied to them.

NTFS reparse points, introduced in NTFS v3, are used by associating a reparse tag in the user space attribute of a file or directory. Microsoft includes several default tags including NTFS symbolic links, directory junction points and volume mount points. When the object manager (see Windows NT line executive) parses a file system name lookup and encounters a reparse attribute, it will reparse the name lookup, passing the user controlled reparse data to every file system filter driver that is loaded into Windows. Each filter driver examines the reparse data to see whether it is associated with that reparse point, and if that filter driver determines a match, then it intercepts the file system call and executes its special functionality.

Starting with Windows Vista Microsoft added the built-in ability to shrink or expand a partition. However, this ability does not relocate page file fragments or files that have been marked as unmovable, so shrinking a volume will often require relocating or disabling any page file, the index of Windows Search, and any Shadow Copy used by System Restore. Various third-party tools are capable of resizing NTFS partitions.

Internally, NTFS uses B-trees to index file system data. Although complex to implement, this allows faster file look up times in most cases. A file system journal is used to guarantee the integrity of the file system metadata but not individual files' content. Systems using NTFS are known to have improved reliability compared to FAT file systems.[46]

NTFS allows any sequence of 16-bit values for name encoding (file names, stream names, index names, etc.) except 0x0000. This means UTF-16 code units are supported, but the file system does not check whether a sequence is valid UTF-16 (it allows any sequence of short values, not restricted to those in the Unicode standard). File names are limited to 255 UTF-16 code units. Certain names are reserved in the volume root directory and cannot be used for files. These are $MFT, $MFTMirr, $LogFile, $Volume, $AttrDef, . (dot), $Bitmap, $Boot, $BadClus, $Secure, $UpCase, and $Extend.[3] (dot) and $Extend are both directories; the others are files. The NT kernel limits full paths to 32,767 UTF-16 code units. There are some additional restrictions on code points and file names.[47]

Causes execution to continue after the data structures in this boot sector.

0x03

8 bytes

"NTFS "Word "NTFS" followed by four trailing spaces (0x20)

OEM ID

This is the magic cookie that indicates this is an NTFS file system.

0x0B

2 bytes

0x0200

Bytes per sector

The number of bytes in a disk sector.

0x0D

1 byte

0x08

Sectors Per Cluster

The number of sectors in a cluster

0x0E

2 bytes

0x0000

Reserved Sectors, unused

How much space is reserved by the OS at the start of disk. This is always 0.

0x10

3 bytes

0x000000

Unused

This field is always 0

0x13

2 bytes

0x0000

Unused by NTFS

This field is always 0

0x15

1 byte

0xF8

Media Descriptor

The type of drive. 0xF8 is used to denote a hard drive (in contrast to the several sizes of floppy).

0x16

2 bytes

0x0000

Unused

This field is always 0

0x18

2 bytes

0x003F

Sectors Per Track

The number of disk sectors in a drive track.

0x1A

2 bytes

0x00FF

Number Of Heads

The number of heads on the drive.

0x1C

4 bytes

0x0000003F

Hidden Sectors

The number of sectors preceding the partition.

0x20

4 bytes

0x00000000

Unused

Not used by NTFS

0x24

4 bytes

0x00800080

Unused

Not used by NTFS

0x28

8 bytes

0x00000000007FF54A

Total sectors

The partition size in sectors.

0x30

8 bytes

0x0000000000000004

$MFT cluster number

The cluster that contains the Master File Table

0x38

8 bytes

0x000000000007FF54

$MFTMirr cluster number

The cluster that contains a backup of the Master File Table

0x40

1 byte

0xF6

Clusters Per File Record Segment

The number of clusters in a File Record Segment. A negative number denotes that the size is 2 to the power of the absolute value. (0xF6 = -10 → 2^10 = 1024).

0x41

3 bytes

0x000000

Unused

This field is not used by NTFS

0x44

1 byte

0x01

Clusters Per Index Buffer

The number of clusters in an Index Buffer. This uses the same algorithm for negative numbers as the "Clusters Per File Record Segment."

0x45

3 bytes

0x000000

Unused

This field is not used by NTFS

0x48

8 bytes

0x1C741BC9741BA514

Volume Serial Number

A unique random number assigned to this partition, to keep things organized.

0x50

4 bytes

0x00000000

Checksum, unused

Supposedly a checksum.

0x54

426 bytes

Bootstrap Code

The code that loads the rest of the operating system. This is pointed to by the first 3 bytes of this sector.

0x01FE

2 bytes

0xAA55

End-of-sector Marker

This flag indicates that this is a valid boot sector.

This boot partition format is roughly based upon the earlier FAT filesystem, but the fields are in different locations. Some of these fields, especially the "sectors per track," "number of heads" and "hidden sectors" fields may contain dummy values on drives where they either don't make sense or aren't determinable.

The OS first looks at the 8 bytes at 0x30 to find the cluster number of the $MFT, then multiplies that number by the number of sectors per cluster (1 byte found at 0x0D). This value is the sector offset (LBA) to the $MFT, which is described below.

In NTFS, all file, directory and metafile data—file name, creation date, access permissions (by the use of access control lists), and size—are stored as metadata in the Master File Table (MFT). This abstract approach allowed easy addition of file system features during Windows NT's development—an example is the addition of fields for indexing used by the Active Directory software. This also enables fast file search software such as Everything to locate named local files and folders included in the MFT very quickly, without requiring any other index.

The MFT structure supports algorithms which minimize disk fragmentation.[50] A directory entry consists of a filename and a "file ID", which is the record number representing the file in the Master File Table. The file ID also contains a reuse count to detect stale references. While this strongly resembles the W_FID of Files-11, other NTFS structures radically differ.

Two copies of the MFT are stored in case of corruption. If the first record is corrupted, NTFS reads the second record to find the MFT mirror file. Locations for both files are stored in the boot sector.[51]

NTFS contains several files that define and organize the file system. In all respects, most of these files are structured like any other user file ($Volume being the most peculiar), but are not of direct interest to file system clients. These metafiles define files, back up critical file system data, buffer file system changes, manage free space allocation, satisfy BIOS expectations, track bad allocation units, and store security and disk space usage information. All content is in an unnamed data stream, unless otherwise indicated.

Duplicate of the first vital entries of $MFT, usually 4 entries (4 Kilobytes).

2

$LogFile

Contains transaction log of file system metadata changes.

3

$Volume

Contains information about the volume, namely the volume object identifier, volume label, file system version, and volume flags (mounted, chkdsk requested, requested $LogFile resize, mounted on NT 4, volume serial number updating, structure upgrade request). This data is not stored in a data stream, but in special MFT attributes: If present, a volume object ID is stored in an $OBJECT_ID record; the volume label is stored in a $VOLUME_NAME record, and the remaining volume data is in a $VOLUME_INFORMATION record. Note: volume serial number is stored in file $Boot (below).

4

$AttrDef

A table of MFT attributes that associates numeric identifiers with names.

5

.

Root directory. Directory data is stored in $INDEX_ROOT and $INDEX_ALLOCATION attributes both named $I30.

6

$Bitmap

An array of bit entries: each bit indicates whether its corresponding cluster is used (allocated) or free (available for allocation).

A file that contains all the clusters marked as having bad sectors. This file simplifies cluster management by the chkdsk utility, both as a place to put newly discovered bad sectors, and for identifying unreferenced clusters. This file contains two data streams, even on volumes with no bad sectors: an unnamed stream contains bad sectors—it is zero length for perfect volumes; the second stream is named $Bad and contains all clusters on the volume not in the first stream.

9

$Secure

Access control list database that reduces overhead having many identical ACLs stored with each file, by uniquely storing these ACLs only in this database (contains two indices: $SII (Standard_Information ID) and $SDH (Security Descriptor Hash), which index the stream named $SDS containing actual ACL table).[11]

10

$UpCase

A table of unicode uppercase characters for ensuring case-insensitivity in Win32 and DOS namespaces.

11

$Extend

A file system directory containing various optional extensions, such as $Quota, $ObjId, $Reparse or $UsnJrnl.

12–23

Reserved for $MFT extension entries. Extension entries are additional MFT records that contain additional attributes that do not fit in the primary record. This could occur if the file is sufficiently fragmented, has many streams, long filenames, complex security, or other rare situations.

These metafiles are treated specially by Windows, handled directly by the NTFS.SYS driver and are difficult to directly view: special purpose-built tools are needed.[52] As of Windows 7, the NTFS driver completely prohibits user access, resulting in a BSoD whenever an attempt to execute a metadata file is made. One such tool is the nfi.exe ("NTFS File Sector Information Utility") that is freely distributed as part of the Microsoft "OEM Support Tools". For example, to obtain information on the "$MFT"-Master File Table Segment the following command is used: nfi.exe c:\$MFT[53] Another way to bypass the restriction is to use 7-zip's file manager and go to the low-level NTFS path \\.\X:\ (where X:\ resembles any drive/partition). Here, 3 new folders will appear: $EXTEND, [DELETED] (a pseudo-folder that 7-zip uses to attach files deleted from the file system to view), and [SYSTEM] (another pseudo-folder that contains all the NTFS metadata files). This trick can be used from removable devices (USB flash drives, external hard drives, SD Cards, etc.) inside Windows, but doing this on the active partition requires offline access (namely WinRE).

For each file (or directory) described in the MFT record, there is a linear repository of stream descriptors (also named attributes), packed together in one or more MFT records (containing the so-called attributes list), with extra padding to fill the fixed 1 KB size of every MFT record, and that fully describes the effective streams associated with that file.

Each attribute has an attribute type (a fixed-size integer mapping to an attribute definition in file $AttrDef), an optional attribute name (for example, used as the name for an alternate data stream), and a value, represented in a sequence of bytes. For NTFS, the standard data of files, the alternate data streams, or the index data for directories are stored as attributes.

According to $AttrDef, some attributes can be either resident or non-resident. The $DATA attribute, which contains file data, is such an example. When the attribute is resident (which is represented by a flag), its value is stored directly in the MFT record. Otherwise, clusters are allocated for the data, and the cluster location information is stored as data runs in the attribute.

For each file in the MFT, the attributes identified by attribute type, attribute name must be unique. Additionally, NTFS has some ordering constraints for these attributes.

There is a predefined null attribute type, used to indicate the end of the list of attributes in one MFT record. It must be present as the last attribute in the record (all other storage space available after it will be ignored and just consists of padding bytes to match the record size in the MFT).

Some attribute types are required and must be present in each MFT record, except unused records that are just indicated by null attribute types.

This is the case for $STANDARD_INFORMATION attribute that is stored as a fixed-size record and containing the timestamps and other basic single-bit attributes (compatible with those managed by FAT in DOS or Windows 9x).

Some attribute types cannot have a name and must remain anonymous.

This is the case for the standard attributes, or for the preferred NTFS "filename" attribute type, or the "short filename" attribute type, when it is also present (for compatibility with DOS-like applications, see below). It is also possible for a file to contain only a short filename, in which case it will be the preferred one, as listed in the Windows Explorer.

The filename attributes stored in the attribute list do not make the file immediately accessible through the hierarchical file system. In fact, all the filenames must be indexed separately in at least one separate directory on the same volume, with its own MFT record and its own security descriptors and attributes, that will reference the MFT record number for that file. This allows the same file or directory to be "hardlinked" several times from several containers on the same volume, possibly with distinct filenames.

The default data stream of a regular file is a stream of type $DATA but with an anonymous name, and the ADSs are similar but must be named.

On the opposite, the default data stream of directories has a distinct type, but are not anonymous: they have an attribute name ("$I30" in NTFS 3+) that reflects its indexing format.

All attributes of a given file may be displayed by using the nfi.exe ("NTFS File Sector Information Utility") that is freely distributed as part of the Microsoft "OEM Support Tools".[53]

Windows system calls may handle alternate data streams.[3] Depending on the operating system, utility and remote file system, a file transfer might silently strip data streams.[3] A safe way of copying or moving files is to use the BackupRead and BackupWrite system calls, which allow programs to enumerate streams, to verify whether each stream should be written to the destination volume and to knowingly skip unwanted streams.[3]

To optimize the storage and reduce the I/O overhead for the very common case of attributes with very small associated value, NTFS prefers to place the value within the attribute itself (if the size of the attribute does not then exceed the maximum size of an MFT record), instead of using the MFT record space to list clusters containing the data; in that case, the attribute will not store the data directly but will just store an allocation map (in the form of data runs) pointing to the actual data stored elsewhere on the volume.[54] When the value can be accessed directly from within the attribute, it is called "resident data" (by computer forensics workers). The amount of data that fits is highly dependent on the file's characteristics, but 700 to 800 bytes is common in single-stream files with non-lengthy filenames and no ACLs.

Some attributes (such as the preferred filename, the basic file attributes) cannot be made non-resident. For non-resident attributes, their allocation map must fit within MFT records.

The format of the allocation map for non-resident attributes depends on its capability of supporting sparse data storage. In the current implementation of NTFS, once a non-resident data stream has been marked and converted as sparse, it cannot be changed back to non-sparse data, so it cannot become resident again, unless this data is fully truncated, discarding the sparse allocation map completely.

When a non-resident attribute is so fragmented, that its effective allocation map cannot fit entirely within one MFT record, NTFS stores the attribute in multiple records. The first one among them is called the base record, while the others are called extension records. NTFS creates a special attribute $ATTRIBUTE_LIST to store information mapping different parts of the long attribute to the MFT records, which means the allocation map may be split into multiple records. The $ATTRIBUTE_LIST itself can also be non-resident, but its own allocation map must fit within one MFT record.

When there are too many attributes for a file (including ADS's, extended attributes, or security descriptors), so that they cannot fit all within the MFT record, extension records may also be used to store the other attributes, using the same format as the one used in the base MFT record, but without the space constraints of one MFT record.

The allocation map is stored in a form of data runs with compressed encoding. Each data run represents a contiguous group of clusters that store the attribute value. For files on a multi-GB volume, each entry can be encoded as 5 to 7 bytes, which means a 1 KB MFT record can store about 100 such data runs. However, as the $ATTRIBUTE_LIST also has a size limit, it is dangerous to have more than 1 million fragments of a single file on an NTFS volume, which also implies that it is in general not a good idea to use NTFS compression on a file larger than 10 GB.[55]

The NTFS file system driver will sometimes attempt to relocate the data of some of the attributes that can be made non-resident into the clusters, and will also attempt to relocate the data stored in clusters back to the attribute inside the MFT record, based on priority and preferred ordering rules, and size constraints.

Since resident files do not directly occupy clusters ("allocation units"), it is possible for an NTFS volume to contain more files on a volume than there are clusters. For example, a 74.5 GB partition NTFS formats with 19,543,064 clusters of 4 KB. Subtracting system files (a 64 MB log file, a 2,442,888-byte Bitmap file, and about 25 clusters of fixed overhead) leaves 19,526,158 clusters free for files and indices. Since there are four MFT records per cluster, this volume theoretically could hold almost 4 × 19,526,158= 78,104,632 resident files.

Opportunistic file locks (oplocks) allow clients to alter their buffering strategy for a given file or stream in order to increase performance and reduce network use.[56] Oplocks apply to the given open stream of a file and do not affect oplocks on a different stream.

Oplocks can be used to transparently access files in the background. A network client may avoid writing information into a file on a remote server if no other process is accessing the data, or it may buffer read-ahead data if no other process is writing data.

Windows NT and its descendants keep internal timestamps as UTC and make the appropriate conversions for display purposes; all NTFS timestamps are in UTC.

For historical reasons, the versions of Windows that do not support NTFS all keep time internally as local zone time, and therefore so do all file systems – other than NTFS – that are supported by current versions of Windows. This means that when files are copied or moved between NTFS and non-NTFS partitions, the OS needs to convert timestamps on the fly. But if some files are moved when daylight saving time (DST) is in effect, and other files are moved when standard time is in effect, there can be some ambiguities in the conversions. As a result, especially shortly after one of the days on which local zone time changes, users may observe that some files have timestamps that are incorrect by one hour. Due to the differences in implementation of DST in different jurisdictions, this can result in a potential timestamp error of up to 4 hours in any given 12 months.[58]

While the different NTFS versions are for the most part fully forward- and backward-compatible, there are technical considerations for mounting newer NTFS volumes in older versions of Microsoft Windows. This affects dual-booting, and external portable hard drives. For example, attempting to use an NTFS partition with "Previous Versions" (a.k.a. Volume Shadow Copy) on an operating system that does not support it will result in the contents of those previous versions being lost.[59] A Windows command-line utility called convert.exe can convert supporting file systems to NTFS, including HPFS (only on Windows NT 3.1, 3.5, and 3.51), FAT16 and FAT32 (on Windows 2000 and later).[60][61]

Mac OS X 10.3 and later include read-only support for NTFS-formatted partitions. The GPL-licensed NTFS-3G also works on Mac OS X through FUSE and allows reading and writing to NTFS partitions. A performance enhanced commercial version, called Tuxera NTFS for Mac,[62] is also available from the NTFS-3G developers. Paragon Software Group sells a read-write driver named NTFS for Mac OS X,[63] which is also included on some models of Seagate hard drives.[64] Native NTFS write support has been discovered in Mac OS X 10.6 and later, but is not activated by default, although workarounds do exist to enable the functionality. However, user reports indicate the functionality is unstable and tends to cause "kernel panics", probably the reason why write support has not been enabled or advertised.[65]

Linux kernel versions 2.2.0 and later include the ability to read NTFS partitions; kernel versions 2.6.0 and later contain a driver written by Anton Altaparmakov (University of Cambridge) and Richard Russon which supports file read, overwrite and resize. Three userspace drivers (NTFSMount, NTFS-3G and Captive NTFS, a 'wrapping' driver that uses Windows' own driver, ntfs.sys) exist for NTFS support. They are built on the Filesystem in Userspace (FUSE), a Linux kernel module tasked with bridging userspace and kernel code to save and retrieve data. All three are licensed under the terms of the GNU General Public License (GPL). Due to the complexity of internal NTFS structures, both the built-in 2.6.14 kernel driver and the FUSE drivers disallow changes to the volume that are considered unsafe, to avoid corruption.[citation needed] Two proprietary solutions also exist:

eComStation, and FreeBSD offer read-only NTFS support (there is a beta NTFS driver that allows write/delete for eComStation, but is generally considered unsafe). A free third-party tool for BeOS, which was based on NTFS-3G, allows full NTFS read and write.

^Since Windows XP, it is very difficult to view a listing of these files: they exist in the root directory's index, but the Win32 interface filters them out. In NT 4.0, the command line dir command would list the metafiles in the root directory if /a were specified. In Windows 2000, dir /a stopped working, but dir /a \$MFT worked.

1.
Software developer
–
A software developer is a person concerned with facets of the software development process, including the research, design, programming, and testing of computer software. Other job titles which are used with similar meanings are programmer, software analyst. According to developer Eric Sink, the differences between system design, software development, and programming are more apparent, even more so that developers become systems architects, those who design the multi-leveled architecture or component interactions of a large software system. In a large company, there may be employees whose sole responsibility consists of one of the phases above. In smaller development environments, a few people or even an individual might handle the complete process. The word software was coined as a prank as early as 1953, before this time, computers were programmed either by customers, or the few commercial computer vendors of the time, such as UNIVAC and IBM. The first company founded to provide products and services was Computer Usage Company in 1955. The software industry expanded in the early 1960s, almost immediately after computers were first sold in mass-produced quantities, universities, government, and business customers created a demand for software. Many of these programs were written in-house by full-time staff programmers, some were distributed freely between users of a particular machine for no charge. Others were done on a basis, and other firms such as Computer Sciences Corporation started to grow. The computer/hardware makers started bundling operating systems, systems software and programming environments with their machines, new software was built for microcomputers, so other manufacturers including IBM, followed DECs example quickly, resulting in the IBM AS/400 amongst others. The industry expanded greatly with the rise of the computer in the mid-1970s. In the following years, it created a growing market for games, applications. DOS, Microsofts first operating system product, was the dominant operating system at the time, by 2014 the role of cloud developer had been defined, in this context, one definition of a developer in general was published, Developers make software for the world to use. The job of a developer is to crank out code -- fresh code for new products, code fixes for maintenance, code for business logic, bus factor Software Developer description from the US Department of Labor

2.
Microsoft
–
Its best known software products are the Microsoft Windows line of operating systems, Microsoft Office office suite, and Internet Explorer and Edge web browsers. Its flagship hardware products are the Xbox video game consoles and the Microsoft Surface tablet lineup, as of 2016, it was the worlds largest software maker by revenue, and one of the worlds most valuable companies. Microsoft was founded by Paul Allen and Bill Gates on April 4,1975, to develop and it rose to dominate the personal computer operating system market with MS-DOS in the mid-1980s, followed by Microsoft Windows. The companys 1986 initial public offering, and subsequent rise in its share price, since the 1990s, it has increasingly diversified from the operating system market and has made a number of corporate acquisitions. In May 2011, Microsoft acquired Skype Technologies for $8.5 billion, in June 2012, Microsoft entered the personal computer production market for the first time, with the launch of the Microsoft Surface, a line of tablet computers. The word Microsoft is a portmanteau of microcomputer and software, Paul Allen and Bill Gates, childhood friends with a passion for computer programming, sought to make a successful business utilizing their shared skills. In 1972 they founded their first company, named Traf-O-Data, which offered a computer that tracked and analyzed automobile traffic data. Allen went on to pursue a degree in science at Washington State University. The January 1975 issue of Popular Electronics featured Micro Instrumentation and Telemetry Systemss Altair 8800 microcomputer, Allen suggested that they could program a BASIC interpreter for the device, after a call from Gates claiming to have a working interpreter, MITS requested a demonstration. Since they didnt actually have one, Allen worked on a simulator for the Altair while Gates developed the interpreter and they officially established Microsoft on April 4,1975, with Gates as the CEO. Allen came up with the name of Micro-Soft, as recounted in a 1995 Fortune magazine article. In August 1977 the company formed an agreement with ASCII Magazine in Japan, resulting in its first international office, the company moved to a new home in Bellevue, Washington in January 1979. Microsoft entered the OS business in 1980 with its own version of Unix, however, it was MS-DOS that solidified the companys dominance. For this deal, Microsoft purchased a CP/M clone called 86-DOS from Seattle Computer Products, branding it as MS-DOS, following the release of the IBM PC in August 1981, Microsoft retained ownership of MS-DOS. Since IBM copyrighted the IBM PC BIOS, other companies had to engineer it in order for non-IBM hardware to run as IBM PC compatibles. Due to various factors, such as MS-DOSs available software selection, the company expanded into new markets with the release of the Microsoft Mouse in 1983, as well as with a publishing division named Microsoft Press. Paul Allen resigned from Microsoft in 1983 after developing Hodgkins disease, while jointly developing a new OS with IBM in 1984, OS/2, Microsoft released Microsoft Windows, a graphical extension for MS-DOS, on November 20,1985. Once Microsoft informed IBM of NT, the OS/2 partnership deteriorated, in 1990, Microsoft introduced its office suite, Microsoft Office

3.
Windows NT 3.1
–
Windows NT3.1 is a 32-bit operating system developed by Microsoft, and released on July 27,1993. It was the first published edition of the Windows NT series of operating systems, Windows NT, however, was a complete, 32-bit operating system that retained a desktop environment familiar to Windows 3.1 users. By extending the Windows brand and beginning Windows NT at version 3.1, the name Windows NT advertised that this was a re-engineered version of Windows. Windows NT began as a rewrite of the OS/2 operating system, for several reasons, including the market success of Windows 3.0 in 1990, Microsoft decided to advance Windows rather than OS/2. They relinquished their OS/2 development responsibilities to IBM, and forked their work on OS/2 v3.0 into an operating system. In 1993, Microsoft marketed two products in the first-generation Windows NT product line, Windows NT3.1 for workstations, and Windows NT3.1 Advanced Server for servers. When these premiered, their sales were limited by high system requirements, Gates hired David N. Cutler arrived at Microsoft on October 31,1988, and work on the future operating system started in November. The operating system was first developed as a version of OS/2. While OS/2 was originally intended to succeed MS-DOS, it had yet to be commercially successful, the OS was to be designed so it could be ported to different processor platforms, and support multiprocessor systems, which few operating systems did at that time. Both Microsoft and IBM wanted to market an operating system that appealed to corporate enterprise software customers and that meant greater security, reliability, processing power, and computer networking features. However, since Microsoft also wanted to market share from Unix on other computing platforms. To this end, Microsoft began by developing and testing their new operating system for a non-x86 processor, alluding to the chips codename, N10, Microsoft codenamed their operating system NT OS/2. DEC preemptively sued Microsoft, alleging that they stole code from Mica for use in the new operating system, in an out-of-court settlement, Microsoft agreed to make NT OS/2 compatible with DECs Alpha processor. The development team estimated that development would be complete within 18 months. By April 1989, the NT OS/2 kernel could run inside the i860 emulator, however, the development team later determined that the i860 was unsuitable for the project. By December they had begun porting NT OS/2 to the MIPS R3000 processor instead, senior Microsoft executive Paul Maritz was targeting a release date in 1992, but the development schedule was uncertain. The company was eager to silence naysayers who speculated that NT wouldnt be on the market until 1994, so, in February 1990, Maritz suggested that Microsoft should demonstrate the OS at the COMDEX computer expo later that year. A few months later, however, a major change delayed that plan, in May 1990, Microsoft released Windows 3.0, a new version of its MS-DOS-based Windows desktop environment

4.
Master boot record
–
The concept of MBRs was publicly introduced in 1983 with PC DOS2.0 operating system. The MBR holds the information on how the partitions, containing file systems, are organized on that medium. This MBR code is referred to as a boot loader. The organization of the table in the MBR limits the maximum addressable storage space of a disk to 2 TiB. Therefore, the MBR-based partitioning scheme is in the process of being superseded by the GUID Partition Table scheme in new computers, a GPT can coexist with an MBR in order to provide some limited form of backward compatibility for older systems. MBRs are not present on non-partitioned media such as floppies, superfloppies or other storage devices configured to behave as such, the original version of the MBR was written by David Litton of IBM in June 1982. The partition table supported up to four primary partitions, of which DOS could only use one and this did not change when FAT16 was introduced as a new file system with DOS3.0. In 1996, support for logical block addressing was introduced in Windows 95B and this also reflected the idea that the MBR is meant to be operating system and file system independent. This was even to the extent of being supported by operating systems for other platforms. Sometimes this was in addition to other pre-existing or cross-platform standards for bootstrapping and partitioning, MBR partition entries and the MBR boot code used in commercial operating systems, however, are limited to 32 bits. Therefore, the disk size supported on disks using 512-byte sectors by the MBR partitioning scheme is limited to 2 TiB. Consequently, a different partitioning scheme must be used for larger disks, the MBR partitioning scheme is therefore in the process of being superseded by the GUID Partition Table. The official approach does little more than ensuring data integrity by employing a protective MBR, specifically, it does not provide backward compatibility with operating systems that do not support the GPT scheme as well. The present non-standard nature of these solutions causes various compatibility problems in certain scenarios, the MBR consists of 512 or more bytes located in the first sector of the drive. It may contain one or more of, A partition table describing the partitions of a storage device, in this context the boot sector may also be called a partition sector. Bootstrap code, Instructions to identify the configured bootable partition, then load, IBM PC DOS2.0 introduced the FDISK utility to set up and maintain MBR partitions. The partitions themselves may also contain data to more complex partitioning schemes, such as extended boot records, BSD disklabels. The MBR is not located in a partition, it is located at a first sector of the device, preceding the first partition

5.
GUID Partition Table
–
All modern PC operating systems support GPT. The widespread MBR partitioning scheme, dating from the early 1980s, one of the main limitations is the usage of 32 bits for storing block addresses and quantity information. For hard disks with 512-byte sectors, the MBR partition table entries allow up to a maximum of 2 TiB, intel therefore developed a new partition table format in the late 1990s as part of what eventually became UEFI. As of 2010, GPT forms a subset of the UEFI specification, GPT allocates 64 bits for logical block addresses, therefore allowing a maximum disk size of 264 sectors. For disks with 512-byte sectors, maximum size is 9.4 ZB or 8 ZiB, mBR-based partition table schemes insert the partitioning information for four primary partitions in the MBR. Like modern MBRs, GPTs use logical block addressing in place of the historical cylinder-head-sector addressing. The protective MBR is contained in LBA0, the GPT header is in LBA1, the UEFI specification stipulates that a minimum of 16,384 bytes, regardless of sector size, be allocated for the Partition Entry Array. On a disk having 512-byte sectors, a partition entry array size of 16,384 bytes, hard-disk manufacturers are transitioning to 4, 096-byte sectors. This was a problem on writes, when the drive is forced to perform two read-modify-write operations to satisfy a single misaligned 4 KB write operation. This is also true of partitions with emulated CHS geometries or partitions accessed only via LBA, extended partitions must start on cylinder boundaries as well. That otherwise unused space is commonly used by bootloaders such as GRUB for storing their second stages. This is referred to as a protective MBR, a single partition type of EEh, encompassing the entire GPT drive, is indicated and identifies it as GPT. While the MBR and protective MBR layouts were defined around 512 bytes per sector, extra space in the MBR typically remains unused. This amounts to a maximum reported size of 2 TB, assuming a disk with 512 bytes per sector, the bootloader in the MBR must not assume a sector size of 512 bytes. The partition table header defines the usable blocks on the disk and it also defines the number and size of the partition entries that make up the partition table. The EFI stipulates a minimum of 16,384 bytes be reserved for the partition table array, so there are 128 partition entries reserved, the header contains the disk GUID. It records its own size and location and the size and location of the secondary GPT header, importantly, it also contains a CRC32 checksum for itself and for the partition table, which may be verified by the firmware, bootloader, or operating system on boot. Because of this, hex editors should not be used to modify the contents of the GPT, such modification would render the checksum invalid

6.
B-tree
–
In computer science, a B-tree is a self-balancing tree data structure that keeps data sorted and allows searches, sequential access, insertions, and deletions in logarithmic time. The B-tree is a generalization of a search tree in that a node can have more than two children. Unlike self-balancing binary search trees, the B-tree is optimized for systems that read, B-trees are a good example of a data structure for external memory. It is commonly used in databases and filesystems, in B-trees, internal nodes can have a variable number of child nodes within some pre-defined range. When data is inserted or removed from a node, its number of child nodes changes, in order to maintain the pre-defined range, internal nodes may be joined or split. Because a range of nodes is permitted, B-trees do not need re-balancing as frequently as other self-balancing search trees. The lower and upper bounds on the number of nodes are typically fixed for a particular implementation. For example, in a 2-3 B-tree, each node may have only 2 or 3 child nodes. Each internal node of a B-tree will contain a number of keys, the keys act as separation values which divide its subtrees. For example, if a node has 3 child nodes then it must have 2 keys, a1. All values in the leftmost subtree will be less than a1, usually, the number of keys is chosen to vary between d and 2 d, where d is the minimum number of keys, and d +1 is the minimum degree or branching factor of the tree. In practice, the take up the most space in a node. The factor of 2 will guarantee that nodes can be split or combined, Each split node has the required minimum number of keys. Similarly, if a node and its neighbor each have d keys. Deleting the key would make the internal node have d −1 keys, the result is an entirely full node of 2 d keys. The number of branches from a node will be one more than the number of stored in the node. In a 2-3 B-tree, the nodes will store either one key or two keys. A B-tree is sometimes described with the parameters — or simply with the highest branching order, a B-tree is kept balanced by requiring that all leaf nodes be at the same depth

7.
Data cluster
–
In computer file systems, a cluster or allocation unit is a unit of disk space allocation for files and directories. To reduce the overhead of managing on-disk data structures, the filesystem does not allocate individual disk sectors by default, on a disk that uses 512-byte sectors, a 512-byte cluster contains one sector, whereas a 4-kibibyte cluster contains eight sectors. A cluster is the smallest logical amount of space that can be allocated to hold a file. Storing small files on a filesystem with large clusters will therefore waste disk space, however, a larger cluster size reduces bookkeeping overhead and fragmentation, which may improve reading and writing speed overall. Typical cluster sizes range from 1 sector to 128 sectors, a cluster need not be physically contiguous on the disk, it may span more than one track or, if sector interleaving is used, may even be discontiguous within a track. This should not be confused with fragmentation, as the sectors are still logically contiguous, the term cluster was changed to allocation unit in DOS4.0. However the term cluster is still widely used

8.
Windows 7
–
Windows 7 is a personal computer operating system developed by Microsoft. It is a part of the Windows NT family of operating systems, Windows 7 was released to manufacturing on July 22,2009, and became generally available on October 22,2009, less than three years after the release of its predecessor, Windows Vista. Windows 7s server counterpart, Windows Server 2008 R2, was released at the same time, Windows 7 continued improvements on Windows Aero with the addition of a redesigned taskbar that allows applications to be pinned to it, and new window management features. Other new features were added to the system, including libraries, the new file sharing system HomeGroup. A new Action Center interface was added to provide an overview of system security and maintenance information. Windows 7 also shipped with updated versions of several applications, including Internet Explorer 8, Windows Media Player. Windows 7 was a success for Microsoft, even prior to its official release. Originally, a version of Windows codenamed Blackcomb was planned as the successor to Windows XP, major features were planned for Blackcomb, including an emphasis on searching and querying data and an advanced storage system named WinFS to enable such scenarios. However, an interim, minor release, codenamed Longhorn, was announced for 2003, by the middle of 2003, however, Longhorn had acquired some of the features originally intended for Blackcomb. Development of Longhorn was also restarted, and thus delayed, in August 2004, a number of features were cut from Longhorn. Blackcomb was renamed Vienna in early 2006, as such, adoption of Vista in comparison to XP remained somewhat low. In July 2007, six months following the release of Vista, it was reported that the next version of Windows would then be codenamed Windows 7. Bill Gates, in an interview with Newsweek, suggested that Windows 7 would be more user-centric, Gates later said that Windows 7 would also focus on performance improvements. Senior Vice President Bill Veghte stated that Windows Vista users migrating to Windows 7 would not find the kind of device compatibility issues they encountered migrating from Windows XP, an estimated 1,000 developers worked on Windows 7. These were broadly divided into core operating system and Windows client experience, in October 2008, it was announced that Windows 7 would also be the official name of the operating system. The first external release to select Microsoft partners came in January 2008 with Milestone 1, at PDC2008, Microsoft demonstrated Windows 7 with its reworked taskbar. On December 27,2008, the Windows 7 Beta was leaked onto the Internet via BitTorrent. According to a performance test by ZDNet, Windows 7 Beta beat both Windows XP and Vista in several key areas, including boot and shutdown time and working with files, such as loading documents

9.
Windows Server 2008 R2
–
Windows Server 2008 R2 is a server operating system produced by Microsoft. It was released to manufacturing on July 22,2009 and launched on October 22,2009, according to the Windows Server Blog, the retail availability was September 14,2009. It is built on the kernel used with the client-oriented Windows 7. It is the first 64-bit–only operating system released from Microsoft, there are seven editions, Foundation, Standard, Enterprise, Datacenter, Web, HPC Server and Itanium, as well as Windows Storage Server 2008 R2. Microsoft introduced Windows Server 2008 R2 at the 2008 Professional Developers Conference as the variant of Windows 7. Two days later, the beta was released to the public via the Microsoft Download Center, on April 30,2009, the release candidate was made available to subscribers of TechNet and MSDN. On May 5,2009, the candidate was made available to the general public via the Microsoft download center. The remaining languages were available around August 11, independent software vendor and independent hardware vendor partners have been able to download Windows Server 2008 R2 from MSDN starting on August 14. Microsoft Partner Program gold/certified members were able to download Windows Server 2008 R2 through the MPP portal on August 19, Volume licensing customers with an existing Software Assurance contracts were able to download Windows Server 2008 R2 on August 19 via the Volume License Service Center. Volume licensing customers without an SA were able to purchase Windows Server 2008 R2 through volume licensing by September 1, additionally, qualifying students have been able to download Windows Server 2008 R2 Standard edition in 15 languages from the Microsoft Imagine program. Microsoft has announced that Server 2008 R2 will be the last version of Windows supporting the Itanium architecture, a reviewer guide published by the company describes several areas of improvement in R2. These include new virtualization capabilities, reduced consumption, a new set of management tools. IIS7.5 has been added to this release also includes updated FTP server services. Security enhancements include encrypted clientless authenticated VPN services through DirectAccess for clients using Windows 7, even though DNSSEC as such is supported, only one signature algorithm is available, #5 / RSA/SHA-1. Since many zones use a different algorithm – including the root zone – this means that in reality Windows still cant serve as a recursive resolver, the DHCP server runs in the context of the Network Service account which has fewer privileges to reduce potential damage if compromised. Windows Server 2008 R2 supports up to 64 physical processors or up to 256 logical processors per system, Server Core includes a subset of the. NET Framework, so that some applications can be used. When raising the forest functional level, the Active Directory recycle bin feature is available, on February 9,2011, Microsoft officially released Service Pack 1 for Windows 7 and Windows Server 2008 R2 to OEM partners. Apart from bug fixes, it introduces two new functions, RemoteFX and Dynamic Memory

10.
Windows 8
–
Windows 8 is a personal computer operating system developed by Microsoft as part of the Windows NT family of operating systems. Development of Windows 8 started before the release of its predecessor, Windows 7 and it was announced at CES2011, and followed by the release of three pre-release versions from September 2011 to May 2012. The operating system was released to manufacturing on August 1,2012, Windows 8 added support for USB3.0, Advanced Format hard drives, near field communications, and cloud computing. Windows 8 was released to a critical reception. Despite these shortcomings,60 million Windows 8 licenses were sold through January 2013, on October 17,2013, Microsoft released Windows 8.1. It addressed some aspects of Windows 8 that were criticized by reviewers and early adopters, Windows 8 was ultimately succeeded by Windows 10 in July 2015. Support for Windows 8 RTM ended on January 12,2016, per Microsoft lifecycle policies regarding service packs, Windows 8.1 must be installed to maintain support, Windows 8 development started before Windows 7 had shipped in 2009. Three milestone releases of Windows 8 leaked to the general public, milestone 1, Build 7850, was leaked on April 12,2011. It was the first build where the text of a window was written centered instead of aligned to the left and it was also probably the first appearance of the Metro-style font, and its wallpaper had the text shhh. Lets not leak our hard work, however, its detailed build number reveals that the build was created on September 22,2010. The leaked copy was Enterprise edition, the OS still reads as Windows 7. Milestone 2, Build 7955, was leaked on April 25,2011, the traditional Blue Screen of Death was replaced by a new black screen, although this was later scrapped. This build introduced a new ribbon in Windows Explorer, Build 7959, with minor changes but the first 64-bit version, was leaked on May 1,2011. The Windows 7 logo was replaced with text displaying Microsoft Confidential. On June 17,2011, build 7989 64-bit edition was leaked and it introduced a new boot screen featuring the same fish as the default Windows 7 Beta wallpaper, which was later scrapped, and the circling dots as featured in the final. It also had the text Welcome below them, although this was also scrapped, on June 1,2011, Microsoft unveiled Windows 8s new user interface, as well as additional features at both Computex Taipei and the D9, All Things Digital conference in California. The Building Windows 8 blog launched on August 15,2011, featuring details surrounding Windows 8s features, Microsoft unveiled more Windows 8 features and improvements on the first day of the Build conference on September 13,2011. Microsoft released the first public build of Windows 8, Windows Developer Preview at the event

11.
Windows Server 2012
–
Windows Server 2012, codenamed Windows Server 8, is the sixth release of Windows Server. It is the version of Windows 8 and succeeds Windows Server 2008 R2. Two pre-release versions, a preview and a beta version, were released during development. The software was available to customers starting on September 4,2012. Unlike its predecessor, Windows Server 2012 has no support for Itanium-based computers, Windows Server 2012 received generally good reviews in spite of having included the same controversial Metro-based user interface seen in Windows 8. The successor to Windows Server 2012, called Windows Server 2012 R2, was released along with Windows 8.1 in October 2013, a service pack, formally designated Windows Server 2012 R2 Update, was released in April 2014. Windows Server 2012, codenamed Windows Server 8, is the release of Windows Server family of operating systems developed concurrently with Windows 8. It was not until April 17,2012 that the announced that the final product name would be Windows Server 2012. Microsoft introduced Windows Server 2012 and its developer preview in the BUILD2011 conference on September 9,2011, however, unlike Windows 8, the developer preview of Windows Server 2012 was only made available to MSDN subscribers. It included a user interface based on Metro design language and a new Server Manager. On February 16,2012, Microsoft released an update for developer preview build that extended its expiry date from April 8,2012 to January 15,2013, before Windows Server 2012 was finalized, two test builds were made public. A public beta version of Windows Server 2012 was released along with the Windows 8 Consumer Preview on February 29,2012, the release candidate of Windows Server 2012 was released on May 31,2012, along with the Windows 8 Release Preview. The product was released to manufacturing on August 1,2012, however, not all editions of Windows Server 2012 were released at the same time. Windows Server 2012 Essentials was released to manufacturing on October 9,2012 and was generally available on November 1,2012. As of September 23,2012, all students subscribed to DreamSpark program can download Windows Server 2012 Standard or Datacenter free of charge, unlike its predecessor, Windows Server 2012 can switch between Server Core and Server with a GUI installation options without a full reinstallation. Server Core – an option with an interface only – is now the recommended configuration. There is also an installation option that allows some GUI elements such as MMC and Server Manager to run. Server Manager has been redesigned with an emphasis on easing management of multiple servers, the operating system, like Windows 8, uses the Metro-based user interface unless installed in Server Core mode

12.
LZ77
–
LZ77 and LZ78 are the two lossless data compression algorithms published in papers by Abraham Lempel and Jacob Ziv in 1977 and 1978. They are also known as LZ1 and LZ2 respectively and these two algorithms form the basis for many variations including LZW, LZSS, LZMA and others. Besides their academic influence, these formed the basis of several ubiquitous compression schemes, including GIF. They are both theoretically dictionary coders, LZ77 maintains a sliding window during compression. This was later shown to be equivalent to the explicit dictionary constructed by LZ78—however, LZ78 decompression allows random access to the input as long as the entire dictionary is available, while LZ77 decompression must always start at the beginning of the input. The algorithms were named an IEEE Milestone in 2004, in the second of the two papers that introduced these algorithms they are analyzed as encoders defined by finite-state machines. A measure analogous to information entropy is developed for individual sequences and this measure gives a bound on the data compression ratio that can be achieved. It is then shown that there exist finite lossless encoders for every sequence that achieve this bound as the length of the sequence grows to infinity, in this sense an algorithm based on this scheme produces asymptotically optimal encodings. This result can be proved more directly, as for example in notes by Peter Shor, LZ77 algorithms achieve compression by replacing repeated occurrences of data with references to a single copy of that data existing earlier in the uncompressed data stream. To spot matches, the encoder must keep track of some amount of the most recent data, such as the last 2 kB,4 kB, or 32 kB. The structure in which data is held is called a sliding window. The encoder needs to keep this data to look for matches, the larger the sliding window is, the longer back the encoder may search for creating references. It is not only acceptable but frequently useful to allow length-distance pairs to specify a length that exceeds the distance. As a copy command, this is puzzling, Go back four characters, how can ten characters be copied over when only four of them are actually in the buffer. Tackling one byte at a time, there is no problem serving this request, because as a byte is copied over, when the copy-from position makes it to the initial destination position, it is consequently fed data that was pasted from the beginning of the copy-from position. The operation is equivalent to the statement copy the data you were given. As this type of pair repeats a single copy of data multiple times, it can be used to incorporate a flexible, then L characters have been matched in total, L>D, and the code is. When the first LR characters are read to the output, this corresponds to a single run unit appended to the output buffer, the pseudocode is a reproduction of the LZ77 compression algorithm sliding window

13.
Windows NT 3.51
–
Windows NT3.51 is the third release of Microsofts Windows NT line of operating systems. It was released on May 30,1995, nine months after Windows NT3.5, the release provided two notable feature improvements, firstly NT3.51 was the first of a short-lived outing of Microsoft Windows on the PowerPC architecture. The second most significant enhancement offered through the release was that it provides support for interoperating with Windows 95. Windows NT4.0 became its successor a year later, the release of Windows NT3.51 was dubbed the PowerPC release at Microsoft. Editions of NT3.51 were also released for the x86, MIPS, new features introduced in Windows NT3. In view of the significant difference in the base, Windows NT3.51 is readily able to run a large number of Win32 applications designed for Windows 95.51 interface. This is probably because 32-bit versions of Internet Explorer 4.0 and later integrated with the Windows 95 desktop, thereafter, up to IE5.0, but no later 5. x versions, were offered. However, the open-source SeaMonkey internet suite does support this flavor of Windows, version 1.1.17 may work out of the box, while version 1.1.19 from 16 March 2010 requires a few manual file updates to work without compromising browsing security. On 26 May 1995, Microsoft released a test version of a refresh, named the Shell Technology Preview. This was the first incarnation of the modern Windows GUI with the Taskbar and it was designed to replace the Windows 3. x Program Manager/File Manager based shell with Windows Explorer-based graphical user interface. The release provided capabilities quite similar to that of the Windows Chicago shell during its late beta phases, however, there was a second public release of the Shell Technology Preview, called Shell Technology Preview Update made available to MSDN and CompuServe users on 8 August 1995. Both releases held Windows Explorer builds of 3.51.1053.1, the Shell Technology Preview program never saw a final release under NT3.51. The entire program was moved across to the Cairo development group who finally integrated the new design into the NT code with the release of NT4.0 in July 1996. Five Service Packs were released for NT3.51, which introduced both bug fixes and new features, Service Pack 5, for example, fixed issues related to the Year 2000 problem. NT3.51 was the last of the series to run on an Intel 80386 processor. This, its ability to use HPFS partitions, and its ability to run at least some of the common control API, means that it still finds a place for occasional use on older machines. Windows NT3.51, like versions of Windows NT3. x, has some compatibility with OS/21. x Applications, however. Supported EIDE addressing schemes include logical block addressing, ONTrack Disk Manager, EZDrive, HPC, Factor Windows NT3.51 Patches & Updates Guide More Information Shell Update Release Shell Update Release

14.
Windows 2000
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Windows 2000 is an operating system for use on both client and server computers. It was produced by Microsoft and released to manufacturing on December 15,1999 and it is the successor to Windows NT4.0, and is the last version of Microsoft Windows to display the Windows NT designation. It is succeeded by Windows XP and Windows Server 2003, during development, Windows 2000 was known as Windows NT5.0. Four editions of Windows 2000 were released, Professional, Server, Advanced Server, and Datacenter Server, Windows 2000 introduces NTFS3.0, Encrypting File System, as well as basic and dynamic disk storage. Support for people with disabilities was improved over Windows NT4.0 with a number of new assistive technologies, the Windows 2000 Server family has additional features including the ability to provide Active Directory services. Windows 2000 can be installed either a manual or unattended installation. Microsoft marketed Windows 2000 as the most secure Windows version ever at the time, however, it became the target of a number of high-profile virus attacks such as Code Red and Nimda. For ten years after its release, it continued to receive patches for security vulnerabilities nearly every month until reaching the end of its lifecycle on July 13,2010. Windows 2000 is a continuation of the Microsoft Windows NT family of operating systems, the original name for the operating system was Windows NT5.0 and its Beta 1 was released in September 1997, followed by Beta 2 in August 1998. On October 27,1998, Microsoft announced that the name of the version of the operating system would be Windows 2000. Windows 2000 Beta 3 was released in January 1999, NT5.0 Beta 1 was similar to NT4.0, including a very similar themed logo. NT5.0 Beta 2 introduced a new boot screen. The new login prompt from the version made its first appearance in Beta 3 build 1946. The new, updated icons first appeared in Beta 3 build 1976, the Windows 2000 boot screen in the final version first appeared in Beta 3 build 1994. Windows 2000 did not have a codename because, according to Dave Thompson of Windows NT team, Windows 2000 Service Pack 1 was codenamed Asteroid and Windows 2000 64-bit was codenamed Janus. During development, there was a build for the Alpha which was abandoned some time after RC1 after Compaq announced they had dropped support for Windows NT on Alpha. From here, Microsoft issued three release candidates between July and November 1999, and finally released the system to partners on December 12,1999. The public could buy the version of Windows 2000 on February 17,2000

15.
Windows XP
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Windows XP is a personal computer operating system that was produced by Microsoft as part of the Windows NT family of operating systems. It was released to manufacturing on August 24,2001, however, in January 2000, both projects were shelved in favor of a single OS codenamed Whistler, which would serve as a single OS platform for both consumer and business markets. Windows XP was an advance from the MS-DOS based versions of Windows in security, stability. It introduced a significantly redesigned graphical user interface and was the first version of Windows to use product activation in an effort to reduce its copyright infringement. Despite some initial concerns over the new licensing model and product activation system, Windows XP eventually proved to be popular and widely used. It is estimated that at least 400 million copies of Windows XP were sold globally within its first five years of availability, sales of Windows XP licenses to original equipment manufacturers ceased on June 30,2008, but continued for netbooks until October 2010. Windows XP remained popular even after the release of newer versions, vistas 2009 successor, Windows 7, only overtook XP in total market share at the end of 2011. Extended support for Windows XP ended on April 8,2014, as of November 2016, Windows XP desktop market share makes it the fourth most popular Windows version after Windows 7, Windows 10 and Windows 8.1. Windows XP is still popular in some countries, Africa as a whole and in Asia, e. g. in China. A number of activity centers were planned, serving as hubs for email communications, playing music, managing or viewing photos, searching the Internet, however, the project proved to be too ambitious. Microsoft discussed a plan to delay Neptune in favor of an interim OS known as Asteroid, which would have been an update to Windows 2000, and since Neptune and Odyssey would be based on the same code-base anyway, it made sense to combine them into a single project. In June 2000, Microsoft began the technical beta testing process, Whistler was expected to be available in Personal, Professional, Server, Advanced Server. At PDC on July 13,2000, Microsoft announced that Whistler would be released during the half of 2001. Build 2257 featured further refinements to the Watercolor theme, along with the introduction of the two-column Start menu. Microsoft released Whistler Beta 1, build 2296, on October 31,2000, build 2410 in January 2001 introduced Internet Explorer 6.0 and the Microsoft Product Activation system. Making it very friendly for the user to use. Builds 2416 and 2419 added the File and Transfer Settings Wizard, on February 5,2001, Microsoft officially announced that Whistler would be known as Windows XP, where XP stands for experience. As a complement, the version of Microsoft Office was also announced as Office XP

16.
Advanced Encryption Standard
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AES is a subset of the Rijndael cipher developed by two Belgian cryptographers, Vincent Rijmen and Joan Daemen, who submitted a proposal to NIST during the AES selection process. Rijndael is a family of ciphers with different key and block sizes, for AES, NIST selected three members of the Rijndael family, each with a block size of 128 bits, but three different key lengths,128,192 and 256 bits. AES has been adopted by the U. S. government and is now used worldwide and it supersedes the Data Encryption Standard, which was published in 1977. The algorithm described by AES is an algorithm, meaning the same key is used for both encrypting and decrypting the data. In the United States, AES was announced by the NIST as U. S. FIPS PUB197 on November 26,2001. This announcement followed a five-year standardization process in which fifteen competing designs were presented and evaluated, AES became effective as a federal government standard on May 26,2002 after approval by the Secretary of Commerce. AES is included in the ISO/IEC 18033-3 standard, unlike its predecessor DES, AES does not use a Feistel network. AES is a variant of Rijndael which has a block size of 128 bits. By contrast, the Rijndael specification per se is specified with block and key sizes that may be any multiple of 32 bits, both with a minimum of 128 and a maximum of 256 bits. AES operates on a 4 ×4 column-major order matrix of bytes, termed the state, most AES calculations are done in a particular finite field. For instance, if there are 16 bytes, b 0, b 1, the number of cycles of repetition are as follows,10 cycles of repetition for 128-bit keys. 12 cycles of repetition for 192-bit keys,14 cycles of repetition for 256-bit keys. Each round consists of processing steps, each containing four similar but different stages. A set of rounds are applied to transform ciphertext back into the original plaintext using the same encryption key. KeyExpansions—round keys are derived from the key using Rijndaels key schedule. AES requires a separate 128-bit round key block for each round plus one more, initialRound AddRoundKey—each byte of the state is combined with a block of the round key using bitwise xor. Rounds SubBytes—a non-linear substitution step where each byte is replaced with another according to a lookup table, shiftRows—a transposition step where the last three rows of the state are shifted cyclically a certain number of steps. MixColumns—a mixing operation which operates on the columns of the state, AddRoundKey Final Round SubBytes ShiftRows AddRoundKey

17.
Windows Server 2003
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Windows Server 2003 is a server operating system produced by Microsoft and released on April 24,2003. It was a successor of Windows 2000 Server and incorporated some of Windows XPs features, an updated version, Windows Server 2003 R2, was released to manufacturing on December 6,2005. Its successor, Windows Server 2008, was released on February 4,2008, Windows Server 2003s kernel was later adopted in the development of Windows Vista. Windows Server 2003 was the follow-up to Windows 2000 Server, incorporating compatibility, unlike Windows 2000 Server, Windows Server 2003s default installation has none of the server components enabled, to reduce the attack surface of new machines. Windows Server 2003 includes compatibility modes to allow applications to run with greater stability. It was made compatible with Windows NT4.0 domain-based networking. Windows Server 2003 brought in enhanced Active Directory compatibility, and better deployment support, to ease the transition from Windows NT4.0 to Windows Server 2003, the product went through several name changes during the course of development. When first announced in 2000, it was known by its codename, Whistler Server, it was named Windows 2002 Server for a time in mid-2001, followed by Windows. NET Server. After Microsoft chose to focus the. NET branding on the. NET Framework, the automated bug checking system was first tested on Windows 2000 but not thoroughly. Amitabh Srivastavas PREfast found 12% of Windows Server 2003s bugs, the remaining 88% being found by computer programmers. Microsoft employs more than 4,700 programmers who work on Windows, Microsoft co-founder Bill Gates stated that Windows Server 2003 was Microsofts most rigorously tested software to date. Microsoft later used Windows Server 2003s kernel in the development of Windows Vista, the following features are new to Windows Server 2003, Internet Information Services v6. The ability to create a disk was removed in favor of Automated System Recovery. Windows Server 2003 Web is meant for building and hosting Web applications, Web pages, terminal Services is not included on Web Edition. However, Remote Desktop for Administration is available, only 10 concurrent file-sharing connections are allowed at any moment. It is not possible to install Microsoft SQL Server and Microsoft Exchange software in this edition without installing Service Pack 1, despite supporting XML Web services and ASP. NET, UDDI cannot be deployed on Windows Server 2003 Web. The. NET Framework version 2.0 is not included with Windows Server 2003 Web, Windows Server 2003 Web supports a maximum of 2 physical processors and a maximum of 2 GB of RAM. However, an instance of Windows Server 2003 Web cannot act as a domain controller, when using it for storage or as a back-end with another remote server as the front-end, CALs may still be required

18.
Operating system
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An operating system is system software that manages computer hardware and software resources and provides common services for computer programs. All computer programs, excluding firmware, require a system to function. Operating systems are found on many devices that contain a computer – from cellular phones, the dominant desktop operating system is Microsoft Windows with a market share of around 83. 3%. MacOS by Apple Inc. is in place, and the varieties of Linux is in third position. Linux distributions are dominant in the server and supercomputing sectors, other specialized classes of operating systems, such as embedded and real-time systems, exist for many applications. A single-tasking system can run one program at a time. Multi-tasking may be characterized in preemptive and co-operative types, in preemptive multitasking, the operating system slices the CPU time and dedicates a slot to each of the programs. Unix-like operating systems, e. g. Solaris, Linux, cooperative multitasking is achieved by relying on each process to provide time to the other processes in a defined manner. 16-bit versions of Microsoft Windows used cooperative multi-tasking, 32-bit versions of both Windows NT and Win9x, used preemptive multi-tasking. Single-user operating systems have no facilities to distinguish users, but may allow multiple programs to run in tandem, a distributed operating system manages a group of distinct computers and makes them appear to be a single computer. The development of networked computers that could be linked and communicate with each other gave rise to distributed computing, distributed computations are carried out on more than one machine. When computers in a work in cooperation, they form a distributed system. The technique is used both in virtualization and cloud computing management, and is common in large server warehouses, embedded operating systems are designed to be used in embedded computer systems. They are designed to operate on small machines like PDAs with less autonomy and they are able to operate with a limited number of resources. They are very compact and extremely efficient by design, Windows CE and Minix 3 are some examples of embedded operating systems. A real-time operating system is a system that guarantees to process events or data by a specific moment in time. A real-time operating system may be single- or multi-tasking, but when multitasking, early computers were built to perform a series of single tasks, like a calculator. Basic operating system features were developed in the 1950s, such as resident monitor functions that could run different programs in succession to speed up processing

19.
Mac OS X 10.3
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Mac OS X Panther is the fourth major release of Mac OS X, Apple’s desktop and server operating system. It followed Mac OS X10.2 and preceded Mac OS X Tiger, Apple released Panther on October 24,2003. Since a New World ROM was required for Mac OS X Panther, third-party software can, however, override checks made during the install process, otherwise, installation or upgrades from Jaguar will fail on these older machines. The Finder icon was also changed, fast User Switching, Allows a user to remain logged in while another user logs in Exposé, Helps the user manage windows by showing them all as thumbnails. TextEdit, TextEdit now is also compatible with Microsoft Word documents, xcode developer tools, Faster compile times with gcc 3.3. It also allows the user to sort fonts into categories, fileVault, On the fly encryption and decryption of a user’s home folder iChat AV, The new version of iChat. Now with built-in Audio- and video-conferencing, X11, X11 is built into Panther Safari, New browser made to replace Internet Explorer for Mac, developed when the contract between Apple and Microsoft ended. Internet Explorer for Mac was still available, Safari 1.0 was included in an update in Jaguar but was used as the default browser in Panther. Microsoft Windows interoperability improvements, including support for Active Directory

20.
Linux kernel
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The Linux kernel is a monolithic Unix-like computer operating system kernel. The Android operating system for computers, smartphones and smartwatches is also based atop the Linux kernel. While the adoption on desktop computers is low, Linux-based operating systems dominate nearly every segment of computing. As of November 2016, all but two of the worlds 500 most powerful supercomputers run Linux, Linux rapidly attracted developers and users who adopted it as the kernel for other free software projects, notably the GNU Operating System. The Linux kernel has received contributions from nearly 12,000 programmers from more than 1,200 companies, the Linux kernel API, the application programming interface through which user programs interact with the kernel, is meant to be very stable and to not break userspace programs. As part of the functionality, device drivers control the hardware. However, the interface between the kernel and loadable kernel modules, unlike in many other kernels and operating systems, is not meant to be stable by design. The Linux kernel, developed by contributors worldwide, is a prominent example of free, day-to-day development discussions take place on the Linux kernel mailing list. The Linux kernel is released under the GNU General Public License version 2, in April 1991, Linus Torvalds, at the time a 21-year-old computer science student at the University of Helsinki, Finland, started working on some simple ideas for an operating system. He started with a task switcher in Intel 80386 assembly language, on 25 August 1991, Torvalds posted the following to comp. os. minix, a newsgroup on Usenet, Im doing a operating system for 386 AT clones. This has been brewing since April, and is starting to get ready, id like any feedback on things people like/dislike in minix, as my OS resembles it somewhat. Ive currently ported bash and gcc, and things seem to work and this implies that Ill get something practical within a few months Yes - its free of any minix code, and it has a multi-threaded fs. It is NOT portable, and it never will support anything other than AT-harddisks, as thats all I have. Its mostly in C, but most people wouldnt call what I write C and it uses every conceivable feature of the 386 I could find, as it was also a project to teach me about the 386. As already mentioned, it uses a MMU, for both paging and segmentation and its the segmentation that makes it REALLY386 dependent. Some of my C-files are almost as much assembler as C, unlike minix, I also happen to LIKE interrupts, so interrupts are handled without trying to hide the reason behind them. After that, many people contributed code to the project, early on, the MINIX community contributed code and ideas to the Linux kernel. At the time, the GNU Project had created many of the components required for an operating system

21.
ReactOS
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ReactOS is a free and open-source operating system for x86/x64 personal computers intended to be binary-compatible with computer programs and device drivers made for Windows Server 2003. Development began in 1996, as a Windows 95 clone project, ReactOS has been noted as a potential open-source drop-in replacement for Windows and for its information on undocumented Windows APIs. As stated on the website, The main goal of the ReactOS project is to provide an operating system which is binary compatible with Windows. Such that people accustomed to the user interface of Windows would find using ReactOS straightforward. The ultimate goal of ReactOS is to allow you to remove Windows, ReactOS is primarily written in C, with some elements, such as ReactOS File Explorer, written in C++. The project partially implements Windows API functionality and has been ported to the AMD64 processor architecture, around 1996, a group of free and open-source software developers started a project called FreeWin95 to implement a clone of Windows 95. The project stalled in discussions of the design of the system, while FreeWin95 had started out with high expectations, there still had not been any builds released to the public by the end of 1997. As a result, the members, led by coordinator Jason Filby. The revived project sought to duplicate the functionality of Windows NT, in creating the new project, a new name, ReactOS, was chosen. The project began development in February 1998 by creating the basis for a new NT kernel, the name ReactOS was coined during an IRC chat. While the term OS stood for operating system, the term referred to the groups dissatisfaction with –. In 2004, a copyright / license violation of ReactOS GPLed code was found when someone distributed a ReactOS fork under the name Ekush OS, in order to avoid copyright prosecution, ReactOS must be expressively completely distinct and non-derivative from Windows, a goal which needs very careful work. A claim was made on 17 January 2006, by now former developer Hartmut Birr on the ReactOS developers mailing list that ReactOS contained code derived from disassembling Microsoft Windows, the code that Birr disputed involved the function BadStack in syscall. S. as well as other unspecified items. Comparing this function to disassembled binaries from Windows XP, Birr argued that the BadStack function was simply copy-pasted from Windows XP, on 27 January 2006, the developers responsible for maintaining the ReactOS code repository disabled access after a meeting was held to discuss the allegations. When approached by NewsForge, Microsoft declined to comment about the incident, contributions from several active ReactOS developers have been accepted post-audit, and low level cooperation for bug fixes still occurs. In a statement on its website, ReactOS cited differing legal definitions of what constitutes clean-room reverse engineering as a cause for the conflict, consequently, ReactOS clarified that its Intellectual Property Policy Statement requirements on clean room reverse engineering conform to US law. Contributors to its development were not affected by events. In September 2007, with the audit nearing completion, the status was removed from the ReactOS homepage

22.
File system
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In computing, a file system or filesystem is used to control how data is stored and retrieved. Without a file system, information placed in a storage medium would be one large body of data with no way to tell where one piece of information stops, by separating the data into pieces and giving each piece a name, the information is easily isolated and identified. Taking its name from the way paper-based information systems are named, the structure and logic rules used to manage the groups of information and their names is called a file system. There are many different kinds of file systems, each one has different structure and logic, properties of speed, flexibility, security, size and more. Some file systems have been designed to be used for specific applications, for example, the ISO9660 file system is designed specifically for optical discs. File systems can be used on different types of storage devices that use different kinds of media. The most common device in use today is a hard disk drive. Other kinds of media that are used include flash memory, magnetic tapes, in some cases, such as with tmpfs, the computers main memory is used to create a temporary file system for short-term use. Some file systems are used on local storage devices, others provide file access via a network protocol. Some file systems are virtual, meaning that the files are computed on request or are merely a mapping into a different file system used as a backing store. The file system access to both the content of files and the metadata about those files. It is responsible for arranging storage space, reliability, efficiency, before the advent of computers the term file system was used to describe a method of storing and retrieving paper documents. By 1961 the term was being applied to computerized filing alongside the original meaning, by 1964 it was in general use. A file system consists of two or three layers, sometimes the layers are explicitly separated, and sometimes the functions are combined. The logical file system is responsible for interaction with the user application and it provides the application program interface for file operations — OPEN, CLOSE, READ, etc. and passes the requested operation to the layer below it for processing. The logical file system manage open file table entries and per-process file descriptors and this layer provides file access, directory operations, security and protection. The second optional layer is the file system. This interface allows support for multiple concurrent instances of physical file systems, the third layer is the physical file system

23.
Windows NT
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Windows NT is a family of operating systems produced by Microsoft, the first version of which was released in July 1993. It is a processor-independent, multiprocessing, multi-user operating system, the first version of Windows NT was Windows NT3.1 and was produced for workstations and server computers. It was intended to complement consumer versions of Windows that were based on MS-DOS, gradually, the Windows NT family was expanded into Microsofts general-purpose operating system product line for all personal computers, deprecating the Windows 9x family. NT was formerly expanded to New Technology but no longer carries any specific meaning, starting with Windows 2000, NT was removed from the product name and is only included in the product version string. NT was the first purely 32-bit version of Windows, whereas its consumer-oriented counterparts, Windows 3. 1x and it is a multi-architecture operating system. Initially, it supported several CPU architectures, including IA-32, MIPS, DEC Alpha, PowerPC, the latest versions support x86 and ARM. This lineage is made clear in Cutlers foreword to Inside Windows NT by Helen Custer and it has been suggested that Dave Cutler intended the initialism WNT as a play on VMS, incrementing each letter by one. However, the project was intended as a follow-on to OS/2 and was referred to as NT OS/2 before receiving the Windows brand. One of the original NT developers, Mark Lucovsky, states that the name was taken from the original target processor—the Intel i860, the letters were dropped from the names of releases from Windows 2000 onwards, though Microsoft described that product as being Built on NT Technology. A main design goal of NT was hardware and software portability, the idea was to have a common code base with a custom Hardware Abstraction Layer for each platform. However, support for MIPS, Alpha, and PowerPC was later dropped in Windows 2000, broad software compatibility was achieved with support for several API personalities, including Windows API, POSIX, and OS/2 APIs – the latter two were phased out starting with Windows XP. Partial MS-DOS compatibility was achieved via an integrated DOS Virtual Machine – although this feature is being phased out in the x86-64 architecture, NT supported per-object access control lists allowing a rich set of security permissions to be applied to systems and services. NT supported Windows network protocols, inheriting the previous OS/2 LAN Manager networking, Windows NT3.1 was the first version of Windows to use 32-bit flat virtual memory addressing on 32-bit processors. Its companion product, Windows 3.1, used segmented addressing, notably, in Windows NT3. x, several I/O driver subsystems, such as video and printing, were user-mode subsystems. In Windows NT4, the video, server, and printer spooler subsystems were moved into kernel mode, NTFS, a journaled, secure file system, was created for NT. Windows NT also allows for other file systems, starting with versions 3.1. Windows NT introduced its own model, the Windows NT driver model. With Windows 2000, the Windows NT driver model was enhanced to become the Windows Driver Model, which was first introduced with Windows 98, but was based on the NT driver model

24.
Linux
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Linux is a Unix-like computer operating system assembled under the model of free and open-source software development and distribution. The defining component of Linux is the Linux kernel, an operating system kernel first released on September 17,1991 by Linus Torvalds, the Free Software Foundation uses the name GNU/Linux to describe the operating system, which has led to some controversy. Linux was originally developed for computers based on the Intel x86 architecture. Because of the dominance of Android on smartphones, Linux has the largest installed base of all operating systems. Linux is also the operating system on servers and other big iron systems such as mainframe computers. It is used by around 2. 3% of desktop computers, the Chromebook, which runs on Chrome OS, dominates the US K–12 education market and represents nearly 20% of the sub-$300 notebook sales in the US. Linux also runs on embedded systems – devices whose operating system is built into the firmware and is highly tailored to the system. This includes TiVo and similar DVR devices, network routers, facility automation controls, televisions, many smartphones and tablet computers run Android and other Linux derivatives. The development of Linux is one of the most prominent examples of free, the underlying source code may be used, modified and distributed‍—‌commercially or non-commercially‍—‌by anyone under the terms of its respective licenses, such as the GNU General Public License. Typically, Linux is packaged in a known as a Linux distribution for both desktop and server use. Distributions intended to run on servers may omit all graphical environments from the standard install, because Linux is freely redistributable, anyone may create a distribution for any intended use. The Unix operating system was conceived and implemented in 1969 at AT&Ts Bell Laboratories in the United States by Ken Thompson, Dennis Ritchie, Douglas McIlroy, first released in 1971, Unix was written entirely in assembly language, as was common practice at the time. Later, in a key pioneering approach in 1973, it was rewritten in the C programming language by Dennis Ritchie, the availability of a high-level language implementation of Unix made its porting to different computer platforms easier. Due to an earlier antitrust case forbidding it from entering the computer business, as a result, Unix grew quickly and became widely adopted by academic institutions and businesses. In 1984, AT&T divested itself of Bell Labs, freed of the legal obligation requiring free licensing, the GNU Project, started in 1983 by Richard Stallman, has the goal of creating a complete Unix-compatible software system composed entirely of free software. Later, in 1985, Stallman started the Free Software Foundation, by the early 1990s, many of the programs required in an operating system were completed, although low-level elements such as device drivers, daemons, and the kernel were stalled and incomplete. Linus Torvalds has stated that if the GNU kernel had been available at the time, although not released until 1992 due to legal complications, development of 386BSD, from which NetBSD, OpenBSD and FreeBSD descended, predated that of Linux. Torvalds has also stated that if 386BSD had been available at the time, although the complete source code of MINIX was freely available, the licensing terms prevented it from being free software until the licensing changed in April 2000

25.
BSD
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Berkeley Software Distribution is a Unix operating system derivative developed and distributed by the Computer Systems Research Group of the University of California, Berkeley, from 1977 to 1995. Today the term BSD is often used non-specifically to refer to any of the BSD descendants which together form a branch of the family of Unix-like operating systems, operating systems derived from the original BSD code remain actively developed and widely used. Historically, BSD has been considered a branch of Unix, Berkeley Unix, because it shared the initial codebase, in the 1980s, BSD was widely adopted by vendors of workstation-class systems in the form of proprietary Unix variants such as DEC ULTRIX and Sun Microsystems SunOS. This can be attributed to the ease with which it could be licensed, FreeBSD, OpenBSD, NetBSD, Darwin, and PC-BSD. The earliest distributions of Unix from Bell Labs in the 1970s included the source code to the system, allowing researchers at universities to modify. A larger PDP-11/70 was installed at Berkeley the following year, using money from the Ingres database project, also in 1975, Ken Thompson took a sabbatical from Bell Labs and came to Berkeley as a visiting professor. He helped to install Version 6 Unix and started working on a Pascal implementation for the system, graduate students Chuck Haley and Bill Joy improved Thompsons Pascal and implemented an improved text editor, ex. Other universities became interested in the software at Berkeley, and so in 1977 Joy started compiling the first Berkeley Software Distribution, 1BSD was an add-on to Version 6 Unix rather than a complete operating system in its own right. Some thirty copies were sent out, some 75 copies of 2BSD were sent out by Bill Joy. 2. 9BSD from 1983 included code from 4. 1cBSD, the most recent release,2. 11BSD, was first issued in 1992. As of 2008, maintenance updates from volunteers are still continuing, a VAX computer was installed at Berkeley in 1978, but the port of Unix to the VAX architecture, UNIX/32V, did not take advantage of the VAXs virtual memory capabilities. 3BSD was also alternatively called Virtual VAX/UNIX or VMUNIX, and BSD kernel images were normally called /vmunix until 4. 4BSD, 4BSD offered a number of enhancements over 3BSD, notably job control in the previously released csh, delivermail, reliable signals, and the Curses programming library. In a 1985 review of BSD releases, John Quarterman et al, many installations inside the Bell System ran 4. 1BSD. 4. 1BSD was a response to criticisms of BSDs performance relative to the dominant VAX operating system, the 4. 1BSD kernel was systematically tuned up by Bill Joy until it could perform as well as VMS on several benchmarks. Back at Bell Labs,4. 1cBSD became the basis of the 8th Edition of Research Unix, to guide the design of 4. The committee met from April 1981 to June 1983, apart from the Fast File System, several features from outside contributors were accepted, including disk quotas and job control. Sun Microsystems provided testing on its Motorola 68000 machines prior to release, the official 4. 2BSD release came in August 1983. On a lighter note, it marked the debut of BSDs daemon mascot in a drawing by John Lasseter that appeared on the cover of the printed manuals distributed by USENIX

26.
Free and open-source
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Free and open-source software is computer software that can be classified as both free software and open-source software. This is in contrast to proprietary software, where the software is under restrictive copyright, the benefits of using FOSS can include decreasing software costs, increasing security and stability, protecting privacy, and giving users more control over their own hardware. Free, open-source operating systems such as Linux and descendents of BSD are widely utilized today, powering millions of servers, desktops, smartphones, Free software licenses and open-source licenses are used by many software packages. In the 1950s, 1960s, and 1970s to 1980s, it was common for users to have the source code for all programs they used. Software, including source code, was shared by individuals who used computers. Most companies had a model based on hardware sales, and provided or bundled software with hardware. Organizations of users and suppliers were formed to facilitate the exchange of software, see, for example, SHARE, by the late 1960s, the prevailing business model around software was changing. In United States vs. IBM, filed 17 January 1969, while some software might always be free, there would be a growing amount of software that was for sale only. Software development for the GNU operating system began in January 1984, an article outlining the project and its goals was published in March 1985 titled the GNU Manifesto. The manifesto included significant explanation of the GNU philosophy, Free Software Definition, the Linux kernel, started by Linus Torvalds, was released as freely modifiable source code in 1991. Initially, Linux was not released under a free or open-source software license, however, with version 0.12 in February 1992, he relicensed the project under the GNU General Public License. Much like Unix, Torvalds kernel attracted the attention of volunteer programmers, freeBSD and NetBSD were released as free software when the USL v. BSDi lawsuit was settled out of court in 1993. OpenBSD forked from NetBSD in 1995, also in 1995, The Apache HTTP Server, commonly referred to as Apache, was released under the Apache License 1.0. In 1997, Eric Raymond published The Cathedral and the Bazaar and this code is today better known as Mozilla Firefox and Thunderbird. Netscapes act prompted Raymond and others to look into how to bring the FSFs free software ideas, the new name they chose was open source, and quickly Bruce Perens, publisher Tim OReilly, Linus Torvalds, and others signed on to the rebranding. The Open Source Initiative was founded in February 1998 to encourage use of the new term, a Microsoft executive publicly stated in 2001 that open source is an intellectual property destroyer. I cant imagine something that could be worse than this for the software business and this view perfectly summarizes the initial response to FOSS by some software corporations. IBM, Oracle, Google and State Farm are just a few of the companies with a serious public stake in todays competitive open-source market, there has been a significant shift in the corporate philosophy concerning the development of free and open-source software

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NTFS-3G
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NTFS-3G is an open source cross-platform implementation of the Microsoft Windows NTFS file system with read-write support. NTFS-3G often uses the FUSE file system interface, so it can run unmodified on many different operating systems. It is runnable on Linux, FreeBSD, NetBSD, OpenSolaris, BeOS, QNX, WinCE, Nucleus, VxWorks, Haiku, MorphOS, Minix, Mac OS X and it is licensed under either the GNU General Public License or a proprietary license. It is a fork of ntfsprogs and is under active maintenance. NTFS-3G was introduced by one of the senior Linux NTFS developers, Szabolcs Szakacsits, the first stable version was released on 2007-02-21 as version 1.0. The developers of NTFS-3G later formed a company, Tuxera Inc. to further develop the code, NTFS-3G is now the free community edition, while Tuxera NTFS is the proprietary version. NTFS-3G supports all operations for writing files, files of any size can be created, modified, renamed, moved, transparent compression is supported, but there is no support for encryption. Support to modify access control lists and permissions is available, NTFS partitions are mounted using the Filesystem in Userspace interface. According to its man page, NTFS-3G supports hard links and symbolic links, NTFS-3G supports partial NTFS journaling, so if an unexpected computer failure leaves the file system in an inconsistent state, the volume can be repaired. As of 2009, a volume having an unclean journal file is recovered and mounted by default, the ‘norecover’ mount option can be used to disable this behavior. Benchmarks show that the performance via FUSE is comparable to that of other filesystems drivers in-kernel. On embedded or old systems, the high usage can severely limit performance. NTFS-3G forked from the Linux-NTFS project on October 31,2006, on February 21,2007, Szabolcs Szakacsits announced the release of the first open source, freely available, stable read/write NTFS driver, NTFS-3G1.0. On October 5,2009, NTFS-3G for Mac was brought under the auspices of Tuxera Ltd. on April 12,2011, it was announced that Ntfsprogs project was merged with NTFS-3G. Ntfsprogs Tuxera NTFS-3G Community Edition NTFS-3G for Mac OS X Writing on NTFS volumes on Mac OS X through NTFS-3G and OS X FUSE for free

28.
MacOS
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Within the market of desktop, laptop and home computers, and by web usage, it is the second most widely used desktop OS after Microsoft Windows. Launched in 2001 as Mac OS X, the series is the latest in the family of Macintosh operating systems, Mac OS X succeeded classic Mac OS, which was introduced in 1984, and the final release of which was Mac OS9 in 1999. An initial, early version of the system, Mac OS X Server 1.0, was released in 1999, the first desktop version, Mac OS X10.0, followed in March 2001. In 2012, Apple rebranded Mac OS X to OS X. Releases were code named after big cats from the release up until OS X10.8 Mountain Lion. Beginning in 2013 with OS X10.9 Mavericks, releases have been named after landmarks in California, in 2016, Apple rebranded OS X to macOS, adopting the nomenclature that it uses for their other operating systems, iOS, watchOS, and tvOS. The latest version of macOS is macOS10.12 Sierra, macOS is based on technologies developed at NeXT between 1985 and 1997, when Apple acquired the company. The X in Mac OS X and OS X is pronounced ten, macOS shares its Unix-based core, named Darwin, and many of its frameworks with iOS, tvOS and watchOS. A heavily modified version of Mac OS X10.4 Tiger was used for the first-generation Apple TV, Apple also used to have a separate line of releases of Mac OS X designed for servers. Beginning with Mac OS X10.7 Lion, the functions were made available as a separate package on the Mac App Store. Releases of Mac OS X from 1999 to 2005 can run only on the PowerPC-based Macs from the time period, Mac OS X10.5 Leopard was released as a Universal binary, meaning the installer disc supported both Intel and PowerPC processors. In 2009, Apple released Mac OS X10.6 Snow Leopard, in 2011, Apple released Mac OS X10.7 Lion, which no longer supported 32-bit Intel processors and also did not include Rosetta. All versions of the system released since then run exclusively on 64-bit Intel CPUs, the heritage of what would become macOS had originated at NeXT, a company founded by Steve Jobs following his departure from Apple in 1985. There, the Unix-like NeXTSTEP operating system was developed, and then launched in 1989 and its graphical user interface was built on top of an object-oriented GUI toolkit using the Objective-C programming language. This led Apple to purchase NeXT in 1996, allowing NeXTSTEP, then called OPENSTEP, previous Macintosh operating systems were named using Arabic numerals, e. g. Mac OS8 and Mac OS9. The letter X in Mac OS Xs name refers to the number 10 and it is therefore correctly pronounced ten /ˈtɛn/ in this context. However, a common mispronunciation is X /ˈɛks/, consumer releases of Mac OS X included more backward compatibility. Mac OS applications could be rewritten to run natively via the Carbon API, the consumer version of Mac OS X was launched in 2001 with Mac OS X10.0. Reviews were variable, with praise for its sophisticated, glossy Aqua interface

Software developer
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A software developer is a person concerned with facets of the software development process, including the research, design, programming, and testing of computer software. Other job titles which are used with similar meanings are programmer, software analyst. According to developer Eric Sink, the differences between system design, software developme

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Mistory software developer group

Microsoft
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Its best known software products are the Microsoft Windows line of operating systems, Microsoft Office office suite, and Internet Explorer and Edge web browsers. Its flagship hardware products are the Xbox video game consoles and the Microsoft Surface tablet lineup, as of 2016, it was the worlds largest software maker by revenue, and one of the wor

1.
Front lobby entrance of building 17, one of the largest buildings on Microsoft's main campus in Redmond

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Paul Allen (l.) and Bill Gates (r.) on October 19, 1981, in a sea of PCs after signing a pivotal contract. IBM called Microsoft in July 1980 inquiring about programming languages for its upcoming PC line; after failed negotiations with another company, IBM gave Microsoft a contract to develop the OS for the new line of PCs.

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Bill Gates giving his deposition in 1998 for the United States v. Microsoft trial.

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In 1996, Microsoft released Windows CE, a version of the operating system meant for personal digital assistants and other tiny computers.

Windows NT 3.1
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Windows NT3.1 is a 32-bit operating system developed by Microsoft, and released on July 27,1993. It was the first published edition of the Windows NT series of operating systems, Windows NT, however, was a complete, 32-bit operating system that retained a desktop environment familiar to Windows 3.1 users. By extending the Windows brand and beginnin

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Screenshot of Windows NT 3.1

Master boot record
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The concept of MBRs was publicly introduced in 1983 with PC DOS2.0 operating system. The MBR holds the information on how the partitions, containing file systems, are organized on that medium. This MBR code is referred to as a boot loader. The organization of the table in the MBR limits the maximum addressable storage space of a disk to 2 TiB. Ther

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Information contained in the Partition Table of an external hard drive as it appears in the utility program QtParted, running under Linux

GUID Partition Table
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All modern PC operating systems support GPT. The widespread MBR partitioning scheme, dating from the early 1980s, one of the main limitations is the usage of 32 bits for storing block addresses and quantity information. For hard disks with 512-byte sectors, the MBR partition table entries allow up to a maximum of 2 TiB, intel therefore developed a

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Diagram illustrating the layout of the GPT scheme. In this example, each logical block is 512 bytes in size, and each partition entry is 128 bytes, and the corresponding partition entries are assumed to be located in LBA 2-33, here. LBA addresses that are negative indicate position from the end of the volume, with −1 as the last addressable block.

B-tree
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In computer science, a B-tree is a self-balancing tree data structure that keeps data sorted and allows searches, sequential access, insertions, and deletions in logarithmic time. The B-tree is a generalization of a search tree in that a node can have more than two children. Unlike self-balancing binary search trees, the B-tree is optimized for sys

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A B Tree insertion example with each iteration. The nodes of this B tree have at most 3 children (Knuth order 3).

Data cluster
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In computer file systems, a cluster or allocation unit is a unit of disk space allocation for files and directories. To reduce the overhead of managing on-disk data structures, the filesystem does not allocate individual disk sectors by default, on a disk that uses 512-byte sectors, a 512-byte cluster contains one sector, whereas a 4-kibibyte clust

Windows 7
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Windows 7 is a personal computer operating system developed by Microsoft. It is a part of the Windows NT family of operating systems, Windows 7 was released to manufacturing on July 22,2009, and became generally available on October 22,2009, less than three years after the release of its predecessor, Windows Vista. Windows 7s server counterpart, Wi

Windows Server 2008 R2
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Windows Server 2008 R2 is a server operating system produced by Microsoft. It was released to manufacturing on July 22,2009 and launched on October 22,2009, according to the Windows Server Blog, the retail availability was September 14,2009. It is built on the kernel used with the client-oriented Windows 7. It is the first 64-bit–only operating sys

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Screenshot of Windows Server 2008 R2 Datacenter Service Pack 1

Windows 8
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Windows 8 is a personal computer operating system developed by Microsoft as part of the Windows NT family of operating systems. Development of Windows 8 started before the release of its predecessor, Windows 7 and it was announced at CES2011, and followed by the release of three pre-release versions from September 2011 to May 2012. The operating sy

Windows Server 2012
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Windows Server 2012, codenamed Windows Server 8, is the sixth release of Windows Server. It is the version of Windows 8 and succeeds Windows Server 2008 R2. Two pre-release versions, a preview and a beta version, were released during development. The software was available to customers starting on September 4,2012. Unlike its predecessor, Windows S

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Windows Server 2012 Start screen

LZ77
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LZ77 and LZ78 are the two lossless data compression algorithms published in papers by Abraham Lempel and Jacob Ziv in 1977 and 1978. They are also known as LZ1 and LZ2 respectively and these two algorithms form the basis for many variations including LZW, LZSS, LZMA and others. Besides their academic influence, these formed the basis of several ubi

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A sign in an Israeli science museum describing the importance of the algorithm

Windows NT 3.51
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Windows NT3.51 is the third release of Microsofts Windows NT line of operating systems. It was released on May 30,1995, nine months after Windows NT3.5, the release provided two notable feature improvements, firstly NT3.51 was the first of a short-lived outing of Microsoft Windows on the PowerPC architecture. The second most significant enhancement

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Windows NT 3.51

Windows 2000
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Windows 2000 is an operating system for use on both client and server computers. It was produced by Microsoft and released to manufacturing on December 15,1999 and it is the successor to Windows NT4.0, and is the last version of Microsoft Windows to display the Windows NT designation. It is succeeded by Windows XP and Windows Server 2003, during de

Windows XP
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Windows XP is a personal computer operating system that was produced by Microsoft as part of the Windows NT family of operating systems. It was released to manufacturing on August 24,2001, however, in January 2000, both projects were shelved in favor of a single OS codenamed Whistler, which would serve as a single OS platform for both consumer and

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Clockwise from top left; Control Panel, Desktop Properties, Command Prompt, Taskbar (at the very bottom) and Microsoft Word

Advanced Encryption Standard
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AES is a subset of the Rijndael cipher developed by two Belgian cryptographers, Vincent Rijmen and Joan Daemen, who submitted a proposal to NIST during the AES selection process. Rijndael is a family of ciphers with different key and block sizes, for AES, NIST selected three members of the Rijndael family, each with a block size of 128 bits, but th

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The SubBytes step, one of four stages in a round of AES

Windows Server 2003
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Windows Server 2003 is a server operating system produced by Microsoft and released on April 24,2003. It was a successor of Windows 2000 Server and incorporated some of Windows XPs features, an updated version, Windows Server 2003 R2, was released to manufacturing on December 6,2005. Its successor, Windows Server 2008, was released on February 4,20

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Screenshot of Windows Server 2003 Enterprise

Operating system
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An operating system is system software that manages computer hardware and software resources and provides common services for computer programs. All computer programs, excluding firmware, require a system to function. Operating systems are found on many devices that contain a computer – from cellular phones, the dominant desktop operating system is

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OS/360 was used on most IBM mainframe computers beginning in 1966, including computers used by the Apollo program.

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The first server for the World Wide Web ran on NeXTSTEP, based on BSD

Mac OS X 10.3
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Mac OS X Panther is the fourth major release of Mac OS X, Apple’s desktop and server operating system. It followed Mac OS X10.2 and preceded Mac OS X Tiger, Apple released Panther on October 24,2003. Since a New World ROM was required for Mac OS X Panther, third-party software can, however, override checks made during the install process, otherwise

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Mac OS X v10.3 Panther

Linux kernel
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The Linux kernel is a monolithic Unix-like computer operating system kernel. The Android operating system for computers, smartphones and smartwatches is also based atop the Linux kernel. While the adoption on desktop computers is low, Linux-based operating systems dominate nearly every segment of computing. As of November 2016, all but two of the w

1.
An iPod booting iPodLinux

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Tux the penguin, mascot of Linux

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An example of Linux kernel panic

ReactOS
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ReactOS is a free and open-source operating system for x86/x64 personal computers intended to be binary-compatible with computer programs and device drivers made for Windows Server 2003. Development began in 1996, as a Windows 95 clone project, ReactOS has been noted as a potential open-source drop-in replacement for Windows and for its information

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The Prime Minister of Russia Dmitry Medvedev (left) being given a demonstration of ReactOS

File system
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In computing, a file system or filesystem is used to control how data is stored and retrieved. Without a file system, information placed in a storage medium would be one large body of data with no way to tell where one piece of information stops, by separating the data into pieces and giving each piece a name, the information is easily isolated and

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Directory listing in a Windows command shell

Windows NT
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Windows NT is a family of operating systems produced by Microsoft, the first version of which was released in July 1993. It is a processor-independent, multiprocessing, multi-user operating system, the first version of Windows NT was Windows NT3.1 and was produced for workstations and server computers. It was intended to complement consumer version

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Windows NT

Linux
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Linux is a Unix-like computer operating system assembled under the model of free and open-source software development and distribution. The defining component of Linux is the Linux kernel, an operating system kernel first released on September 17,1991 by Linus Torvalds, the Free Software Foundation uses the name GNU/Linux to describe the operating

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Linus Torvalds, principal author of the Linux kernel

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Ubuntu, a popular Linux distribution

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5.25-inch floppy discs holding a very early version of Linux

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Nexus 5 running Android

BSD
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Berkeley Software Distribution is a Unix operating system derivative developed and distributed by the Computer Systems Research Group of the University of California, Berkeley, from 1977 to 1995. Today the term BSD is often used non-specifically to refer to any of the BSD descendants which together form a branch of the family of Unix-like operating

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BSD

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The DEC VT100 terminal, widely used for Unix timesharing

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The VAX-11/780, a typical minicomputer used for early BSD timesharing systems

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VAX-11/780 internals

Free and open-source
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Free and open-source software is computer software that can be classified as both free software and open-source software. This is in contrast to proprietary software, where the software is under restrictive copyright, the benefits of using FOSS can include decreasing software costs, increasing security and stability, protecting privacy, and giving

NTFS-3G
–
NTFS-3G is an open source cross-platform implementation of the Microsoft Windows NTFS file system with read-write support. NTFS-3G often uses the FUSE file system interface, so it can run unmodified on many different operating systems. It is runnable on Linux, FreeBSD, NetBSD, OpenSolaris, BeOS, QNX, WinCE, Nucleus, VxWorks, Haiku, MorphOS, Minix,

1.
NTFS-3G

MacOS
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Within the market of desktop, laptop and home computers, and by web usage, it is the second most widely used desktop OS after Microsoft Windows. Launched in 2001 as Mac OS X, the series is the latest in the family of Macintosh operating systems, Mac OS X succeeded classic Mac OS, which was introduced in 1984, and the final release of which was Mac

1.
Comparison of acoustic spectrograms of a song in an uncompressed format and lossy formats. That the lossy spectrograms are different from the uncompressed one indicates that they are, in fact, lossy, but nothing can be assumed about the effect of the changes on perceived quality.

3.
Recording of single magnetisations of bits on a 200 MB HDD-platter (recording made visible using CMOS-MagView).

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HDD with disks and motor hub removed exposing copper colored stator coils surrounding a bearing in the center of the spindle motor. Orange stripe along the side of the arm is thin printed-circuit cable, spindle bearing is in the center and the actuator is in the upper left